FEB    6  1912 
GIFT 


LIBRARY 


University  of  California. 

•3IFT  OF  -  ^^-^^^  ^^S^ 
Class 


V.     I 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

Microsoft  Corporation 


http://www.archive.org/details/dryergeographyOOdryerich 


HIGH   SCHOOL 

GEOGRAPHY 

PHYSICAL,    ECONOMIC,    AND 
REGIONAL 


BY 
CHARLES   REDWAY   DRYER,   F.G.S.A.,  F.R.G.S. 

)| 
PROFESSOR  OF  GEOGRAPHY  AND  GEOLOGY,  INDLVNA  STATE  NORMAL  SCHOOL 
AUTHOR  OF  "  LESSONS  IN  PHYSICAL  GEOGRAPHY  " 


Parts  I.  and  II. 
PHYSICAL    AND    ECONOMIC 


>.»  .  >   ,  ■';  ; ,'» 


AMERICAN    BOOK    COMPANY 

NEW  YORK        .-.         CINCINNATI         .-.         CHICAGO 


frvu>'(Jl-ti. 


Copyright,  ign,  by 
CHARLES    REDWAY    DRYER 


Entered  at  Stationers'  Hall,  London 


Dr.  H.  S.  Geog. 
w.  p.  1. 


PREFACE 

That  the  better  part  of  geography  is  to  be  found  in  a  study  of 
relationships  is  the  conviction  of  all  geographers.  Only  by  such 
study  can  an  aihrmative  answer  be  given  to  Jowett's  question, 
*'Can  geography  be  used  to  make  students  think?"  There  is 
no  subject  which  presents  a  greater  number  and  variety  of 
relationships  than  geography.  It  leaves  hardly  any  field  of 
human  knowledge  untouched,  and  is  the  mutual  debtor  and 
creditor  of  all.  It  is  capable  of  yielding  a  purely  scientific 
discipline  ''uncontaminated  with  the  worship  of  usefulness," 
and  it  can  be  made  as  baldly  ''practical"  as  the  commercial 
spirit  requires.  The  higher  interests  of  education  demand  a 
judicious  combination  of  pure  and  applied  science. 

The  most  important  thing  about  the  earth  is  the  fact  that  it 
is  a  human  planet,  that  men  not  only  five  upon  it,  but  make, 
somehow,  a  living  out  of  it.  The  earth  as  a  planet,  a  machine 
which  "goes"  and  "works,"  an  organism  which  has  grown  and 
developed  in  the  past  and  will  continue  to  do  so  in  the  future, 
has  never  been  so  thoroughly  studied  and  understood  as  it  is 
to-day.  The  main  result  of  such  study,  under  the  name  of 
physical  geography,  has  been  a  favorite  subject  in  secondary 
schools.  Some  special  phases  of  human  activity,  more  or  less 
closely  related  to  the  earth,  such  as  products,  manufactures, 
trade,  races,  customs,  language,  religion,  and  government,  are 
everywhere  taught  under  the  names  of  commercial  and  political 
geography.  But  these  different  kinds  of  geography  are  seldom 
brought  closely  together,  and  the  crowning  relationship  of  all 
geographic  science,  the  relation  of  the  human  species  to  its 
natural  environment,  is  generally  missed  or  but  dimly  seen. 

To  get  a  view  of  the  earth,  not  only  as  the  home  of  man,  but 
as  the  garden  in  which  he  has  grown,  the  school  in  which  he  has 

s 

228747 


6  c.  f  i/\  y ;  -e . ;  • :  Preface 

been  educated  and  civilized,  the  environment  in  which  still 
higher  ideals  may  be  attained,  is  the  object  of  modern  geograph- 
ical study.  This  can  be  accompHshed  only  by  taking  an  eco- 
nomic standpoint,  from  which  the  dependence  of  human  Hfe  upon 
natural  conditions  and  the  influence  of  those  conditions  upon 
human  life  can  be  most  clearly  seen.  This  book  is  an  attempt 
to  present  such  a  view  and  to  treat  the  leading  facts  and  prin- 
ciples of  geography  as  factors  in  the  human  struggle  for  a  better 
Hving,  that  is,  for  the  highest  possible  civilization.  Physical 
geography,  a  view  of  the  earth  as  it  would  be  if  no  man  had  ever 
lived  upon  it,  forms  the  necessary  basis.  The  first  part  of  this 
book  is  called  physical  geography  because  the  principal  subject 
discussed  in  it  is  the  natural  earth,  but  the  treatment  is  more 
brief  than  in  many  recent  textbooks.  Many  topics  of  great 
interest  to  the  student  of  pure  science  are  omitted  or  lightly 
touched,  preference  being  given  to  those  features  and  processes 
which  have  directly  "helped  or  hindered  man  in  his  progress." 
The  fact  is  constantly  kept  in  mind  that  man  is  himself  a  part 
of  nature  and  the  picture  is  painted  from  the  beginning  against 
a  strong  background  of  human  hfe. 

The  second  part  is  called  economic  geography  because  the 
point  of  view  is  reversed,  and  the  outlines  of  household  manage- 
ment practiced  by  the  great  human  family  in  its  terrestrial 
home  are  presented  against  the  background  of  the  natural  earth 
already  shown.  It  is  hoped  that  by  this  method  of  treatment 
the  pecuHar  interest  and  value  of  physical  geography  will  not 
be  lost,  while  its  use  as  a  foundation  for  economic  geography 
will  give  added  attraction  and  stability  to  both.  Parts  I  and  II 
are  planned  to  furnish  as  much  material  as  can  be  used  in  a 
high  school  course  of  five  or  six  months. 

For  those  schools  which  devote  a  longer  period  to  the  study 
of  geography.  Part  III  furnishes  a  more  detailed,  intimate,  and 
graphic  study  of  the  same  theme.  The  natural  earth  is  still  the 
basis  and  is  divided  into  natural  provinces  arranged  in  a  few 
groups,  forming  typical  environments  in  which  the  economic 
adaptations  of  human  life  must  be  broadly  similar,  varying  only 


PREFACE  7 

with  the  stage  of  civilization  of  the  inhabitants.  Where  the 
civilization  of  a  natural  environment  is  not  native,  but  has  been 
introduced  from  some  other  more  favorable  environment,  inter- 
esting contrasts  appear;  but  in  every  case  the  possibilities  are 
strictly  limited  by  natural  conditions.  North  America  is  found 
to  present  all  the  typical  natural  environments  of  the  world 
except  the  strictly  equatorial.  A  detailed  discussion  of  these 
with  references,  more  or  less  extended,  to  similar  environments 
in  other  parts  of  the  world,  serves  to  bring  out  all  the  principal 
kinds  of  adaptation  to  natural  environment  which  the  human 
race  has  achieved,  and  gives  a  bird's-eye  view  of  world  economies. 
This  part  of  the  book  comes  near  to  being  a  concrete  example 
of  a  recent  definition  of  economic  geography  as  ''the  study  of 
the  different  types  of  environments  in  the  relations  they  bear  to 
the  activities  of  human  life. " 

The  treatment  by  natural  rather  than  by  political  and,  conse- 
quently, artificial  divisions  is  attended  by  no  serious  difficulty 
except  in  the  handling  of  statistics,  which  are  always  compiled 
according  to  political  units.  The  result  is  some  slight  want  of 
exactness  in  figures,  but  as  these  are  constantly  changing,  the 
defect  is  not  great.  The  author  recognizes  the  fact  that  such 
treatment  is  an  innovation  in  some  degree  revolutionary;  but 
he  believes  that  the  advantage  it  gives  in  showing  the  essential 
relationships  of  geography  more  than  compensates  for  all  diffi- 
culties, and  that  when  once  understood  it  will  be  accepted  and 
welcomed. 

Reports  of  committees  of  the  National  Educational  Association 
and  of  the  Association  of  American  Geographers  have  recently 
outlined  in  some  detail  courses  in  geography  for  secondary  schools. 
While  this  book  has  not  been  written  on  the  plan  of  conforming 
to  the  requirements  of  either,  it  will  be  found  to  cover  substan- 
tially the  ground  of  both. 

An  unusual  number  and  variety  of  maps  have  been  introduced 
in  the  hope  of  leading  teachers  and  students  to  a  better  apprecia- 
tion and  use  of  this  unrivaled  method  of  geographical  expression. 


TABLE    OF    CONTENTS 

PART  I.     PHYSICAL  GEOGRAPHY 

Chapter  Page 

I.   Earth,  Sun,  and  Moon 9 

II.  The  Plan  of  the  Earth 24 

III.  World  Economy 32 

IV.  The  Land 36 

V.   Gradation  by  Running  Water 72 

VT.  The  Economic  Relations  of  Streams 95 

VIL   Gradation  by  Ice 113 

VIII.   Standing  Water 1 24 

IX.   Gradation  by  Ground  Water  and  Wind 132 

X.   Soils 139 

XL  The  Sea 150 

XII.   Coasts  and  Ports 160 

XIII.  The  Atmosphere 172 

XIV.  Moisture  in  the  Air 193 

XV.   Climate 217 

XVI.   Plant  Regions 226 

XVII.  The  Geography  of  Animals 243 

XVIII.  The  Human  Species 255 

PART  II.  ECONOMIC  GEOGRAPHY 

XIX.  Natural  Resources  and  Food  Supply 263 

XX.   Clothing  and  Constructive  Materials 289 

XXI.  Heat,  Light,  and  Power 308 

XXIL   Manufacture,  Trade,  and  Transportation 318 

List  of  Important  Maps 328 

Index 329 

8 


PART   I.     PHYSICAL    GEOGRAPHY 


CHAPTER    I 


EARTH,   SUN,  AND   MOON 


ATMOSPHERE 


The  Earth  is  a  globular  mass  of  rock,  water,  and  air,  tied  to 
the  sun  by  gravitation  and  revolving  around  it  at  a  distance  of 
about  93,000,000  miles.  The  core  or  central  body  of  the  earth 
is  probably  a  solid  ball  of  hot  nickel-iron,  with  an  outer  crust 
largely  composed  of  oxygen  and  siHcon  combined  with  other 
elements  to  form 
various  kinds  of 
rocks.  The  whole 
sohd  earth  may  be 
called  the  rock 
sphere  (lithosphere) . 
The  depressions  in 
the  crust  are  occu- 
pied by  a  thin  sheet 
of  water  which  covers  nearly  three  fourths  of  its  surface  and 
constitutes  the  water  sphere  (hydrosphere).  The  rock  and  water 
spheres  are  surrounded  and  inclosed  by  an  atmosphere  of  nitro- 
gen, oxygen,  and  other  gases,  the  extent  of  which  is  not  definitely 
known. 


Section  of  part  of  the  earth. 


The  atmosphere  is  as  truly  a  part  of  the  earth  as  the  rock,  but  this  fact 
is  often  disregarded  and  the  word  earth  is  used  to  mean  only  the  solid  and 
liquid  mass.  In  this  sense  the  earth  is  a  slightly  compressed  spheroid,  its 
polar  diameter  being  7,899.6  miles,  its  equatorial  diameter  7,926.6  miles, 
and  its  circumference  about  24,900  miles. 

Men  do  not  live  upon  the  surface  of  the  earth,  which  is  the  outer  surface 

9 


lO  PHYSICAL  GEOGRAPHY 

of  the  atmosphere,  but  hundreds  of  miles  below,  on  or  near  the  surface  of 
the  rock  and  water  spheres,  which  is  commonly  called  the  face  of  the  earth. 

The  Sun  is  a  bright  star,  about  no  times  the  diameter  of  the 
earth.  The  body  of  the  sun  is  surrounded  by  an  atmosphere 
consisting  of  white-hot  vapors  of  various  metals,  which  radiate 
heat  and  light  in  every  direction.  The  heat  and  light  from  the 
sun  penetrate  the  earth's  atmosphere  and  reach  the  land  and 
water.  The  earth  rotates  on  its  shortest  axis  once  in  24  hours, 
thus  exposing  different  sides  to  the  sun  and  causing  an  alterna- 
tion of  sunlight  and  shadow,  or  day  and  night.  The  rotation 
of  the  earth  is  clearly  shown  by  the  apparent  movement  of  the 
stars  from  east  to  west. 

Latitude  and  Longitude.  —  The  earth's  rotation  not  only 
divides  time  into  short  periods  of  light  and  darkness,  but  also 
furnishes  fixed  points  from  which  to  measure  distances  and  fix 
locations. 

If  a  mark  is  made  upon  the  surface  of  a  smooth,  uniformly  colored  ball, 
it  is  impossible  to  describe  its  position  for  want  of  other  points  of  reference. 
If  the  ball  is  set  to  spinning  like  a  top,  the  rotation  establishes  an  axis  and 
two  poles  at  opposite  ends  of  it.  A  line  may  be  drawn  around  the  ball 
midway  between  the  poles  which  will  be  an  equator,  or  divider  of  the  surface 
into  two  equal  parts.  A  line  may  also  be  drawn  from  pole  to  pole  at  right 
angles  to  the  equator.  Then  the  position  of  any  point  on  the  ball  may 
be  determined  and  described  by  its  angular  distance  from  each  of  these 
lines.    This  is  the  meaning  and  purpose  of  latitude  and  longitude. 

Latitude  (breadth)  is  angular  distance  from  the  equator  toward 
each  pole  and  is  measured  in  degrees  up  to  90  degrees.  Longitude 
(length)  is  angular  distance  from  a  line  arbitrarily  fixed  at  right 
angles  to  the  equator,  each  way  around  to  the  opposite  side  of 
the  earth,  and  is  measured  in  degrees  up  to  180  degrees.  For 
convenience  a  set  of  lines  is  imagined  or  drawn  parallel  Vvdth 
the  equator,  called  parallels,  and  another  set  at  right  angles  to 
the  equator,  called  meridians.  These  lines  form  a  network, 
which  divides  the  face  of  the  earth  into  quadrangles  indispen- 
sable in  surveying  and  mapping. 


EARTH,  SUN,  AND  MOON 


II 


Polaris 


Fig.  2.  — Parallels  and  meridians. 

The  number  of  parallels  and  meridians  is  unlimited.  Portions  of  some 
of  them  are  surveyed  and  located  on  the  ground  and  form  boundaries  of 
states,  counties,  townships,  and  sections.  They  are  drawn  upon  a  map  at 
any  convenient  distance  apart,  and  the  network  is  used  to  locate  the 
desired  features.  The  meridian  passing  through  Gireenwich,  near  London, 
is  now  used  as  a  base  line  or  prime  meridian  throughout  the  world.  The 
axis  of  the  earth  always  maintains  the  same  direction  in  space,  the  north 
end  of  it  looking  toward  a  point  in  the 
heavens  near  the  star  Polaris,  "the  north 
star."  To  an  observer  at  the  equator  Polaris 
is  on  the  northern  horizon  (Fig.  3) ;  but  if  he 
travels  northward  the  star  rises  higher  above 
the  horizon  until  at  the  north  pole  it  is 
directly  overhead.  Hence  directions  and  lati- 
tude may  be  determined  by  observing  the 
stars. 

The  Seasons.  —  The  earth  revolves 
around  the  sun  in  a  nearly  circular 
orbit,  requiring  a  little  more  than  365 
days  to  complete  one  revolution.  The 
revolution  of  the  earth  may  be  seen 
by  noticing  that  the  groups  of  stars  visible  at  any  given  hour 
of  the  night  change  from  week  to  week,  and  month  to  month.  If 
the  axis  of  the  earth  were  perpendicular  to  the  plane  of  its  orbit, 
its  revolution  would  bring  no  change  except  in  the  appearance 
of  the  heavens  at  night,  and  would  be  of  little  importance;  for 
in  that  case  the  line  dividing  the  lighted  side  of  the  earth  from 
the  dark  side  would  always  pass  through  the  poles,  half  of  the 


Fig.  3. 


/ 

■1^9 

-■■  ^^1 

IHHlSi^ 

"%. 

'  ^    i 

^9^ 

^ 

■     ^ 

't 

'""'        '^^U& 

■I 

'"%. 

p^ 

W"^ 

K 

'p.^  ^SWj^y 

\ 

/^^         i 

■ '  "^ 

\ 

^^H^^^^^^^^I^^'^^T^^'^^^l 

'/ 

Fig.  4.  —  Position  of  the  northern  hemisphere  throughout  the  year. 


f^^^ 


Fig.  5.  —  (From  Todd's  New  Astronomy.) 
12 


EARTH,    SUN,   AND,  MOON 


13 


northern  and  half  of  the  southern  hemisphere  would  always  be 
in  the  Hght,  and  day  and  night  would  be 
everywhere  and  always  of  equal  length, 
as  in  Fig.  6  B.  But  the  earth's  axis  is 
inclined  about  23°  30'  from  a  perpendic- 
ular to  the  plane  of  its  orbit,  and  always 
in  the  same  direction.  As  the  earth 
moves  around  the  sun,  the  northern  and 
southern  hemispheres  are  turned  toward 
the  sun  alternately  and  each  in  turn 
receives  more  than  an  equal  share  of 
sunlight,  as  in  Fig.  6  A  and  C  When 
either  hemisphere  is  turned  toward  the 
sun,  every  place  in  it  is  in  sunhght  more 
than  half  the  time,  and  the  days  are 
longer  than  the  nights.  When  it  is  turned 
away  from  the  sun  the  reverse  is  true. 

Fig.  4  shows  the  conditions  in  the  northern 
hemisphere  for  each  month  of  the  year.  Fig.  5 
shows  the  apparent  path  of  the  sun  in  the 
heavens  at  different  seasons  in  middle  northern 
latitudes.  The  long  path  of  the  sun  above  the 
horizon  in  summer  brings  long  days  and  a  warm 
season;  the  short  path  in  winter  brings  short  days  and  a  cold  season. 

The  sun's  rays  have  greater  heating  power  at  noon  than  in 
the  morning  or  evening  because  they  then  pass  through  less  air, 

NOON 


Fi-.  6. 


strike  the  earth  more  nearly  at  right  angles,  and  are  spread  over 
less  surface  (Fig.  7).     When  the  days  are  long  the  sun's  rays 


14  PHYSICAL   GEOGRAPHY 

are  more  nearly  direct  and  their  heating  power  is  greater  than 
when  the  days  are  short.  Thus  the  incHnation  of  the  earth's 
axis  brings  about  a  variation  in  the  length  of  the  day  and  in 
the  angle  of  the  sun's  rays,  and  these  changes  work  together  to 
make  the  months  successively  warmer  or  colder. 

The  most  important  points  in  this  cycle  of  changes  are:  (i)  The  vernal 
equinox,  M.dii(^h  21,  when  the  sun  is  vertical  at  the  equator  and  shines  to 
either  pole.  The  days  and  nights  are  everywhere  of  equal  length  and  the 
angle  of  the  sun's  rays  is  the  same  at  corresponding  latitudes  in  both  hemi- 
spheres. (2)  The  summer  solstice,  June  22,  when  the  sun  is  vertical  at  the 
tropic  of  Cancer,  23°  30'  north  of  the  equator,  and  shines  23°  30'  beyond 
the  north  pole  to  the  Arctic  circle.  In  the  northern  hemisphere  the  days 
are  longer  and  the  sun's  rays  more  direct  than  at  any  other  date.  (3)  The 
autumnal  equinox,  September  23,  when  the  conditions  are  the  same  as  at 
the  vernal  equinox;  (4)  The  winter  solstice,  December  22,  when  the  sun's 
rays  are  vertical  at  the  tropic  of  Capricorn,  23°  30'  south  of  the  equator, 
shine  23°  30'  beyond  the  south  pole  to  the  Antarctic  circle,  and  fall  short 
of  reaching  the  north  pole.  In  the  northern  hemisphere  the  days  are 
shorter  and  the  sun's  rays  are  more  slanting  than  at  any  other  date.  The 
change  of  conditions  from  one  of  these  dates  to  the  next  is  gradual. 

The  inequahty  of  day  and  night  and  the  variation  in  the 
angle  of  the  sun's  rays  increase  toward  the  poles;  therefore 
the  contrast  between  summer  and  winter  increases  in  the  same 
direction.  The  presence  of  permanent  ice  and  snow  in  the  polar 
regions  renders  the  seasonal  differences  there  less  than  they 
otherwise  would  be.  Between  the  tropics  the  differences  of 
temperature  are  sHght  and*  the  seasons  are  distinguished  as  wet 
(summer)  and  dry  (winter).  The  year  of  four  strongly  marked 
seasons  is  found  only  in  middle  latitudes. 

Economic  Relations.  —  The  light  and  heat  of  the  sun  furnish 
the  energy  which  keeps  things  alive  and  moving  on  the  earth. 
The  supply  is  not  continuous  and  uniform,  but  subject  to  the 
interruptions  of  day  and  night  and  the  variations  of  the  seasons. 
Plants  and  animals  are  very  sensitive  to  these  changes,  which 
impose  upon  them  alternating  periods  of  activity  and  rest. 
Outside  the  polar  regions,  every  space  of  24  hours  is  divided 


EARTH,    SUN,   AND   MOON  1 5 

into  a  period  of  daylight  and  a  period  of  darkness.  In  daylight 
plants  and  animals,  including  man,  are  generally  active  in 
obtaining  food  and  acquiring  whatever  is  necessary  or  desired 
for  subsistence.  Darkness  is  generally  a  period  of  rest  during 
which  they  assimilate  food,  build  up  tissue,  repair  waste,  and 
renew  strength.  For  men  the  regular  and  frequent  recurrence 
of  periods  of  sleep,  preferably  during  the  hours  of  darkness,  is 
absolutely  necessary  to  health  and  efficiency. 

The  influence  of  change  of  seasons  upon  plants  is  very  great.  In  equa- 
torial regions  vegetation  is  luxuriant  at  all  times,  but  alternations  of  wet 
and  dry  periods  induce  some  variation  in  the  rate  of  growth.  Where  the 
contrast  of  seasons  is  strong,  more  than  half  the  plants  pass  the  cold  or 
dry  season  in  the  form  of  seed,  and  more  than  half  the  animals  live  less  than 
a  year.  Many  animals  live  over  the  winter  by  migrating  to  a  warmer 
region,  by  using  the  food  stored  during  the  summer,  or  by  lying  torpid. 
Men  whose  occupation  is  directly  dependent  upon  plants,  as  farmers  and 
gardeners,  do  little  through  the  winter,  or  change  their  'work. 

Solar  and  Civil  Days.  —  The  rotation  and  revolution  of  the 
earth  furnish  two  units  for  reckoning  time,  the  day  and  the 
year.  The  period  from  the  moment  when  the  sun  reaches  his 
highest  point  in  the  heavens  and  is  on  the  meridian,  to  the 
moment  when  he  next  reaches  the  same  point,  varies  from  day 
to  day.  The  average  length  of  this  period  is  divided  into  the 
hours,  minutes,  and  seconds  shown  by  ordinary  clocks  and 
watches.  For  convenience  the  ordinary  or  civil  day  is  made 
to  begin  and  end  at  midnight,  and  is  of  the  same  length  in  every 
part  of  the  world.  Inside  the  polar  circles  the  civil  day  does  not 
always  correspond  to  actual  day  and  night,  since  the  time  from 
sunrise  to  sunset  varies  from  a  few  minutes  to  six  months. 

If  the  earth's  face  were  plane,  sunrise,  noon,  and  sunset  would  each 
occur  over  every  part  of  it  at  the  same  moment,  but  as  the  spheroidal  earth 
rotates,  sunrise,  noon,  and  sunset  travel  continuously  westward  at  the 
rate  of  15  degrees  of  longitude  every  hour.  When  it  is  noon  at  Greenwich 
it  is  about  7.00  a.m.  at  New  York,  6.00  at  St.  Louis,  5.00  at  Denver,  and 
4.00  at  San  Francisco.  So  each  meridian  has  its  own  sun  time,  slower 
and  earlier  than  the  meridians  east  of  it,  faster  and  later  than  those  west 


i6 


PHYSICAL  GEOGRAPHY 


of  it.     The  longitude  of  any  place  may  be  measured  by  the  difference  of 
time  between  it  and  Greenwich,  one  degree  for  every  four  minutes. 

Standard  Time.  —  For  people  who  stay  at  home  their  own 
local  mean  sun  time  is  the  most  convenient;  but  for  travelers, 
and  especially  for  railroad  companies,  it  is  advantageous  to 


STANDARD  TIME 
BELTS 


Fig.  8. 

adopt  standard  meridians  15°,  or  one  hour,  apart,  and  to  use 
the  time  of  each  meridian  over  a  certain  area  on  each  side  of  it. 
In  North  America  five  standard  time  belts  are  in  use:  Atlantic 
or  60th  meridian  time  (four  hours  slower  than  Greenwich  time), 
Eastern  or  75th  meridian  time.  Central  or  90th  meridian  time. 
Mountain  or  105th  meridian  time,  and  Pacific  or  120th  meridian 
time.  The  boundaries  of  these  belts  are  irregular.  When  a 
traveler  crosses  the  boundary  of  a  time  belt,  he  sets  his  watch 
forward,  or  back,  one  hour.  Nearly  all  civilized  countries  have 
adopted  standard  time  meridians. 

International  Date  Line.  —  If  one  travels  westward,  sun  time  becomes 
slower  at  the  rate  of  one  hour  for  every  15  degrees  of  longitude,  and  in 
going  around  the  earth  a  watch  must  be  set  back,  in  all,  24  hours,  which 
would  cause  the  traveler  to  lose  one  day  from  his  calendar.    If  he  travels 


EARTH,   SUN,   AND  MOON 


17 


eastward,  sun  time  grows  faster  at  the  same  rate,  and  a  watch  must  be 
set  ahead  to  correspond.  Thus  one  would  add  a  day  to  his  calendar. 
Hence  it  is  found  necessary  to  fix  upon  an  arbitrary  line  for  the  correction 
of  the  calendar.  This  is  called  the  international  date  line,  and  for  all 
vessels  is  the  meridian  of  180°.  Whenever  a  ship  crosses  this  line  to  the 
westward,  a  day  is  added  to  the  reckoning,  but  if  to  the  eastward,  a  day 
is  dropped  from  it. 

The  Calendar.  —  The  calendar  now  in  use  in  most  of  the 
civilized  world  was  adopted  by  Pope  Gregory  XIII  in  1582. 
The  earth  completes  one  revolution  around  the  sun  in  365  d.  5  h. 
48  m.  46  s.  The  calendar  is  made  to  agree  approximately  with 
the  solar  year  by  having  three  successive  years  of  365  days  each 
and  then  a  leap  year  of  366  days.  An  extra  day  added  every 
fourth  year  is  a  little  too  much,  and  therefore  century  years, 
like  1900  and  2000,  are  leap  years  only  when  divisible  by  400. 

The  Moon,  Month,  and  Week.  —  The  division  of  the  year 
into  months  and  weeks  was  originally  suggested  by  the  changes 


'''"^■^  /earthI  third 

UARTER  ItAKlMl  QUARTERN 


FULL 
MOON 


y 


Phases  as  seen  from  above  moon's  orbit. 


O 


O 


o 


y 


MOON 

Phases  as  seen  from  the  earth. 


Fig.  9. 


/ 


of  the  moon.     The  moon  revolves  around  the  earth  from  west 
to  east  in  about  29I  days.     When  it  is  between  the  earth  and 


1 8  PHYSICAL  GEOGRAPHY 

the  sun  the  dark  side  is  turned  toward  us  and  is  called  new  moon 
(Fig.  9).  About  a  week  later  half  of  the  lighted  side  is  visible 
and  is  called  first  quarter.  When  the  moon  is  on  the  opposite 
side  of  the  earth  from  the  sun  its  lighted  side  is  turned  toward 
us  and  is  called  full  moon.  Then  again,  about  a  week  later,  half 
the  lighted  side  is  visible  and  is  called  last  quarter.  The  inter- 
vals between  these  changes  are  variable,  but  average  about  seven 
days.  The  calendar  weeks  and  months  do  not  coincide  with 
the  periods  or  phases  of  the  moon,  and  the  number  of  days  in 
successive  months  varies  in  an  arbitrary  and  irregular  manner. 

The  year  is  naturally  divided  by  the  solstices  and  equinoxes  into  four 
seasons:  spring,  March  21  to  June  22,  93  days;  summer,  June  22  to  Sep- 
tember 23,  93  days;  autumn,  September  23  to  December  22,  90  days;  win- 
ter, December  22  to  March  21,  89  or  90  days.  Although  the  Gregorian 
calendar  is  imperfectly  adjusted  to  the  natural  time  periods  of  day,  week, 
month,  and  year,  any  change  in  it  would  cause  so  much  disturbance  and 
confusion  as  to  make  it  undesirable,  if  not  impossible. 

Maps  and  Map  Projections.  —  The  special  means  of  expression 
in  geography  is  the  map,  because  a  map  shows  the  facts  of  dis- 
tribution better  than  anything  else  can.  A  map  is  a  drawing 
which  shows  the  position,  direction,  distance,  and  area  of  objects 
upon  a  horizontal  plane,  as  though  a  portion  of  the  earth's  sur- 
face were  stripped  off,  spread  out  flat,  and  reduced  in  size.  The 
one  thing  essential  for  a  good  map  is  that  the  position  of  every 
feature  shown  be  located  correctly;  if  this  is  done,  the  direc- 
tions, distances,  and  areas  will  be  correct.  No  absolutely  cor- 
rect map  of  any  portion  of  the  earth's  surface  can  be  drawn, 
because  it  is  impossible  to  flatten  a  spherical  surface  into  a 
plane  surface  without  distorting  it. 

The  indispensable  basis  and  guide  in  the  construction  of  a  map  is  the 
network  of  parallels  and  meridians.  Numerous  projections  or  plans  for 
drawing  the  parallels  and  meridians  are  in  common  use.  Some  show  the 
forms  more  correctly  than  others,  some  distort  forms  for  the  sake  of  show- 
ing areas  correctly,  while  others  are  very  erroneous  as  to  forms  and  areas 
but  correct  as  to  directions.  The  best  maps  for  common  use  are  designed 
to  show  forms,  areas,  and  directions  with  as  little  error  as  possible. 


MAPS  AND   MAP   PROJECTIONS 


19 


The  orthographic  projection  (Fig.  10)  is  a  picture  of  a  globe  as  it  appears 
from  a  distance  many  times  its  diameter.  Straight  parallel  hnes,  projected 
through  the  parallels  and  meridians  of  the  globe  upon  a  plane  surface  per- 
pendicular to  them,  locate  the  network  of  the  map.  Such  a  map  is  correct 
near  the  center,  but  around  the  edges  the  areas  are  greatly  reduced. 


Fig.  10.  —  Orthographic  projection 


Fig.  II.  —  Stereographic  projection. 


The  stereo  graphic  projection  (Fig.  11)  is  a  picture  of  a  transparent  hemi- 
sphere as  it  would  appear  to  the  eye  placed  at  the  middle  point  of  the 
surface  of  the  opposite  hemisphere. 
In  this  map  the  areas  are  reduced 
near  the  center  and  enlarged  to- 
ward the  edges. 

The  globular  projection 
(Fig.  1 2)  is  a  picture  of  a  trans- 
parent hemisphere  as  it  would 
appear  to  the  eye  placed  at  a 
distance  1.707  times  the  radius 
of  the  sphere  from  its  center. 
In  this  map  the  parallels  along 
any  meridian  and  the  meridi- 
ans along  any  parallel  are  very 
nearly  equidistant.     It  shows  ^'^-  "-gio^"^'-  projection, 

both  form  and  area  with  less  error  than  any  other  projection,  and 


20 


PHYSICAL  GEOGRAPHY 


is  especially  advantageous  for  maps  of  the  hemispheres  used  in 
teaching. 

In  the  cylindrical  projection  the  surface  of  the  sphere  is  con- 
ceived to  be  that  of  a  cyHnder  of  the  same  diameter,  cut  length- 
wise and  flattened  out. 
The  meridians  are  straight, 
parallel,  and  equidistant. 
If  the  parallels  are  pro- 
jected stereographically, 
the  length  of  the  cylinder 
is  twice  the  diameter  of  the 
sphere  (Fig.  13^),  and  areas 
are    increasingly    exagger- 

Fig.  13,  — Cylindrical  projections.  atcd  tOWard  the  polcS. 

Mercator^s  projection  (Figs.  13  ^  and  14)  is  cyHndrical,  but  the 
parallels  are  so  spaced  that  the  degrees  of  latitude  are  propor- 
tional to  the  degrees  of  longitude.  It  is  the  only  projection  on 
which  directions  are  abso- 
lutely correct,  and  hence  it  is 
much  used  by  sailors.  It  is 
the  best  for  maps  of  winds 
and  ocean  currents  in  which 
true  directions  are  required. 
CyHndrical  projections  have 
the  advantage  of  showing  all 
the  more  important  parts  of 
the  earth  upon  one  contin- 
uous sheet,  but  on  account 
of  the  enormous  exaggeration 
and  distortion  of  areas  in  the 
higher  latitudes,  they  should 
never  be  used  in  teaching  children  and  should  always  be  corrected 
by  reference  to  a  globe. 

Mollweide^s  equal-area  projection   (Fig.  16)  shows  the  whole 
face  of  the  earth  upon  one  continuous  sheet,  one  hemisphere  in 


100° 


110°  120"^  100'=  80''  00°. 

Fig.  14.—  Mercator's  projection. 


MAPS   AND   MAP   PROJECTIONS 


21 


the  center  and  half  of  the  other  on  each  side.  Near  the  cen- 
ter forms  are  but  sUghtly  distorted  and  distances  are  nearly 
correct.  In  the  marginal  portions  distortion  is  considerable, 
and  north-south  distances  are  exaggerated;  but  this  projection 
has  the  advantage  of  show- 
ing areas  correctly.  Hence 
it  is  used  for  maps  in  which 
a  comparison  of  areas  is  im- 
portant. 

In  the  conical  projection 
(Fig.  15)  the  surface  repre- 
sented is  conceived  to  be  that 
of  a  cone  cut  lengthwise  and 
flattened  out.    The  parallels  F^g-  is.— conicai  projection, 

are  arcs  of  equidistant,  concentric  circles,  and  the  meridians  are 
radiating  straight  lines  intersecting  the  parallels  at  right  angles. 
For  areas  of  no  great  extent  in  latitude,  such  as  the  United  States, 
a  map  on  this  projection  is  very  nearly  correct. 

Map  Scales.  —  The  scale  of  a  map  is  the  ratio  which  distances  and  areas 
on  the  map  bear  to  the  actual  distances  and  areas  on  the  earth.  Scales 
are  expressed  by  ratios,  as  i  :  i,ooo,ocx),  which  means  that  one  inch  on 
the  map  corresponds  to  one  million  inches  on  the  earth;  or  in  linear  units, 
as  I  inch  =  i  mile;  or  by  graduated  lines.  For  small  areas  the  scale  may 
be  large,  one  foot  or  more  to  the  mile;  for  large  areas  it  must  be  small.  On 
maps  of  large  areas  no  uniform  scale  can  apply  exactly  to  all  parts. 


RELIEF  OF  I 

{After  d 


DEPTHS 

0  to  OGO  ft, 

OGO  ft.  to  13,100  ft. 

13,100  ft.  to  19,700  ft. 

Below   19,700  ft. 


22 


I 


ITH  CRUST 

•tonne) 


HEIGHTS 
Below  Sea  Level  to  990  ft.  above 
990  ft.  to  3,300  ft. 
3,300  ft.  to  13,100  ri. 
Above  13.100  ft. 


CHAPTER  II 

THE  PLAN  OF  THE  EARTH 

The  Earth  Crust.  —  If  the  water  were  out  of  the  way  so 
that  the  whole  surface  of  the  earth  crust  could  be  seen,  two 
contrasted  areas  would  appear.  One  third  of  it  is  a  broad, 
irregular,  elevated  table  or  platform,  roughened  by  mountains, 
plateaus,  hills,  and  valleys.  The  rest  of  it  is  a  steep-sided, 
smooth-bottomed  depression,  lying  about  2J  miles  below  the 
elevated  surface.  The  elevated  area  is  the  continental  platform, 
and  the  depressed  area  is  the  oceanic  basin.  The  highest  point 
known  (Mt.  Everest  in  central  Asia)  is  29,000  feet  above  sea 
level,  and  the  lowest  point  known  (Nero  Deep,  near  the  Ladrone 
Islands,  western  Pacific  Ocean)  is  31,614  feet  below  sea  level. 
The  difference  or  range  of  elevation  is  about  iif  miles. 

This  is  only  one  seven-hundredth  part  of  the  iliameter  of  the  solid  earth, 
and  if  represented  upon  a  globe  seven  feet  in  diameter  would  be  about 
one  eighth  of  an  inch.  The  earth  crust  is  much  smoother  in  proportion 
to  its  size  than  the  skin  of  an  orange. 

The  Margin  of  the  Continental  Platform.  —  The  sea  water  not 
only  fills  the  oceanic  basin  full,  but  also  spreads  out  over  the 
lower  part  of  the  continental  platform  until  the  outer  edge  of 
the  platform  is  about  660  feet  under  water.  The  continents 
and  large  islands  all  stand  upon  the  platform  and  are  bordered 
by  a  belt  of  shallow  water  (Fig.  16).  The  lowlands  less  than 
660  feet  above  water,  and  the  adjacent  continental  shej  less 
than  660  feet  under  water,  constitute  an  unstable  portion  of 
the  earth  crust  which  has  risen  and  sunk  many  times.  Where 
the  slope  is  so  gentle,  sHght  movements  up  or  down  make  great 
changes  in  the  outlines  and  area  of  the  land. 

24 


THE   PLAN  OF   THE   EARTH  2$ 

If  the  crust  should  rise  660  feet,  the  shore  line  would  recede  to  the 
outer  edge  of  the  shelf  and  the  total  land  area  would  be  increased  about 
20  per  cent.  If  the  crust  should  sink  660  feet,  the  shore  line  would  advance 
upon  the  land  and  about  30  per  cent  of  the  present  land  area  would  be 
flooded  by  the  sea.  Much  greater  up-and-down  movements  than  these 
have  occurred  in  the  past.  Rivers  carry  down  the  waste  of  the  land  and 
deposit  it  upon  the  continental  shelf,  spreading  out  material  for  the  rock 
strata  of  new  lands  which  may  sometime  rise  from  the  sea.  The  shallow 
waters  of  the  shelf  are  the  home  of  abundant  plant  and  animal  life,  and  the 
site  of  the  great  fishing  grounds  of  the  world.  Because  of  the  shallowness 
tides  rise  higher  along  the  shores  than  they  do  in  deep  water,  and  make  it 
possible  for  large  ships  to  reach  ports  hke  Montreal,  Glasgow,  and  London, 
situated  far  up  the  bays  and  rivers.  The  relations  of  the  continental  shelf 
to  the  land  and  its  inhabitants  are  far  closer  than  those  of  the  deep  ocean 
basins. 

Arrangement  of  the  Great  Crust  Features.  —  The  continental 
platform  which  supports  the  great  land  masses  forms  a  nearly 
continuous  belt  around  the  earth  at  about  70°  N.  Lat.  (Fig.  16). 
From  this  belt  three  arms  extend  southward,  the  American  to 
about  57°  S.  Lat.,  the  Eurafrican  to  about  37°  S.  Lat.,  and 
the  Asia-Australian  to  about  45°  S.  Lat.  An  Antarctic  con- 
tinent of  undefined  extent  surrounds  the  south  pole.  The 
oceanic  basin  forms  a  continuous  belt  around  the  earth  at 
about  60°  S.  Lat.,  from  which  three  arms  extend  northward, 
interlocking  with  the  continental  arms.  Of  these  the  Pacific 
basin  is  roughly  circular  in  outline,  the  Atlantic  arm  is  long, 
narrow,  and  S-shaped,  while  the  Indian  arm  is  short  and 
broadly  triangular.  The  Arctic  basin  occupies  an  area  around 
the  north  pole,  the  limits  of  which  are  not  accurately  known. 
Each  continental  arm  is  broken  nearly  midway  of  its  length  by 
a  cross  projection  of  the  oceanic  basin,  the  American  by  the 
Gulf  of  Mexico  and  Caribbean  Sea,  the  Eurafrican  by  the  Medi- 
terranean Sea,  and  the  Asia-AustraHan  by  the  straits  of  the 
Indian  archipelago. 

Land  and  Water  Hemispheres.  —  About  70  per  cent  of  the  land  lies 
north  of  the  equator  and  about  86  per  cent  of  the  sea  lies  south  of  it.  If 
a  map  of  a  hemisphere  is  drawn  with  London  as  a  center,  it  will  include 


26 


PHYSICAL  GEOGRAPHY 


about  82.5  per  cent  of  all  the  land,  and  the  opposite  hemisphere  with  its 
center  near  New  Zealand  will  include  about  63  per  cent  of  all  the  sea.  The 
land  hemisphere  thus  drawn  is  46.7  per  cent  land,  and  the  water  hemisphere 
is  90  per  cent  sea  (Figs.  17  and  18). 


Fig.  17.  Fig.  18. 

The  Arrangement  of  Land  Masses.  —  The  continental  land 
masses  conform  roughly  to  the  position  and  shape  of  the  con- 
tinental platform  and  are  thus  divided  into  seven  continents, 

Europe,  Asia,  and  North 
America  lying  close  together  in 
the  northern  hemisphere;  South 
America,  Africa,  Australia,  and 
Antarctica  lying  wholly  or  partly 
in  the  southern  hemisphere,  and 
more  widely  separated  from  one 
another. 

If  a  globe  is  viewed  in  such  a  posi- 
tion that  the  center  of  Asia  (E.  Long. 
90°,  N.  Lat.  50°)  is  the  center  of 
the  visible  hemisphere  (Fig.  19),  it 
will  be  seen  that  the  other  continents 
are  arranged  around  Asia  with  some 
approach  to  symmetry.  Europe  is  but  a  large  peninsula  projecting  west- 
ward.    Africa  lies  close  against  the  southwestern  shores  of  Eurasia,  and 


THE   PLAN  OF  THE  EARTH  27 

is  tied  to  it  by  the  Isthmus  of  Suez  and  the  shelf  at  the  mouth  of  the  Red 
Sea.  Directly  northward  of  Asia,  across  the  narrow  polar  basin,  lies  North 
America,  connected  by  the  shelf  of  Bering  Sea  and  Strait.  To  the  east 
of  south  the  submarine  platform  of  the  Malay  archipelago  stretches  away 
to  Australia.  In  past  ages  America  and  Austraha  have  been  connected 
with  Asia,  and  Africa  with  Europe,  by  land  bridges,  and  to-day  every  part 
of  the  continental  lands  except  Antarctica  can  be  reached  from  Asia  with- 
out crossing  a  strait'  more  than  250  miles  wide.  The  central  position  of 
Asia  and  the  continuity  of  the  radiating  arms  of  the  continental  platform, 
furnishing  easy  routes  of  travel  to  nearly  all  habitable  lands,  have  been 
of  great  importance  in  controlling  the  migration  and  dispersal  of  plants, 
animals,  and  men.  There  would  be  no  insuperable  difficulty  in  building 
a  continuous  railroad  from  Cape  Horn  to  the  Cape  of  Good  Hope,  with 
branch  lines  to  Liverpool  and  Lisbon,  while  Australia  could  be  connected 
with  the  system  by  a  short  ocean  ferry. 

Eastern  and  Western  Hemispheres.  —  The  earth  has  been 
somewhat  arbitrarily  divided  into  an  Eastern  and  a  Western 
Hemisphere.  In  the  Eastern  Hemisphere  Europe,  Asia,  and 
Africa  compose  the  "  Old  World ";  in  the  Western  Hemi- 
sphere North  and  South  America  are  called  the  "  New  World." 
There  is  no  reason  to  think  that  any  part  of  the  land  of  the  Old 
World  is  actually  older  than  some  parts  of  the  New  World. 
The  human  species  probably  originated  in  Asia,  and  the  earliest 
records  of  human  history  are  found  in  Asia  and  Africa,  but 
Australia  was  not  discovered  by  Europeans  until  100  years 
after  the  discovery  of  America  by  Columbus.  Asia  and  Europe 
form  physically  one  continuous  land  mass  and  are  often  treated 
as  one  continent  under  the  name  of  Eurasia,  but  for  historic 
reasons  geographers  usually  regard  them  as  distinct. 

Northern  and  Southern  Continents.  —  The  continents  natu- 
rally fall  into  two  groups  which  are  strongly  contrasted  in  physical 
characters,  in  their  relations  to  plant  and  animal  life,  and  in  the 
part  they  play  in  human  history.  About  four  fifths  of  the  area 
of  the  northern  continents  lies  in  those  temperate  latitudes  which 
are  most  favorable  for  the  development  of  human  faculties; 
while  about  four  fifths  of  the  area  of  the  southern  continents 
lies  in  the  hot  belts,  between  the  parallels  of  latitude  30°  north 


28  PHYSICAL   GEOGRAPHY. 

and  south,  where  the  climate  is  oppressive  and  plants  and 
animals  are  either  absent  on  account  of  aridity,  or  are  able  on 
account  of  humidity  to  compete  successfully  with  man  in  the 
struggle  for  possession.  The  southern  continents  are  isolated 
from  the  northern  and  from  one  another  and  are  relatively  in- 
accessible. They  contain  less  than  one  eighth  of  the  world's 
population.  Consequently  they  are  in  their  human  relations, 
as  well  as  in  their  physical  conditions,  subordinate  appendages 
of  the  great  northern  land  masses. 

Asia.  —  The  central  and  largest  continent  spreads  a  vast 
expanse  from  the  equator  far  into  the  polar  regions,  too  shapeless 
to  suggest  any  geometrical  figure.  The  eastern  side  presents 
to  the  Pacific  a  belt  of  mountainous  peninsulas  and  off-shore 
islands,  which  border  the  shelf  for  6,cx)o  miles.  The  southern 
margin  is  cut  by  deep  notches  into  three  massive  peninsulas. 
On  the  west  it  is  imperfectly  separated  from  Europe  by  the 
Black  and  Caspian  basins,  and  other  depressions  which  once 
connected  them  with  the  Arctic  Ocean.  On  the  north  low  plains 
slope  gently  to  the  icy  sea.  The  body  of  the  continent  consists 
of  a  mass  of  plateaus  and  mountains,  the  loftiest  in  the  world, 
the  culminating  core  of  which  is  Tibet. 

From  the  Tibetan  center,  highlands  trend  southeastward  toward  Aus- 
tralia, northeastward  toward  America,  westward  into  Europe,  and  south- 
westward  into  Africa.  The  average  elevation  of  Asia  is  3,120  feet,  25  per 
cent  of  it  is  below  660  feet,  and  14  per  cent  is  above  6,600  feet.  Asia 
contains  30  per  cent  of  all  the  land  and  more  than  half  of  all  the  people  on 
the  globe. 

Europe,  a  westward  projection  from  Asia  between  the  Arctic 
Ocean  and  the  Mediterranean  Sea,  is  characterized  by  many 
peninsulas  and  inclosed  seas,  which  penetrate  far  into  the  in- 
terior. These  give  it  the  longest  coast  line  in  proportion  to 
its  area  of  all  the  continents,  and  furnish  unequaled  facilities 
for  travel  and  trade  by  water.  The  highlands  of  Asia  are  pro- 
longed through  southern  Europe  by  less  lofty  ranges  of  folded 
mountains  to  the  shores  of  the  Atlantic.     These  are  flanked  by 


THE  PLAN   OF   THE   EARTH  29 

plateaus  and  lesser  ranges  of  moderate  height.  In  the  north- 
west the  rugged  peninsula  of  Scandinavia  presents  a  bold  front 
to  the  sea.  The  body  of  the  continent  is  a  low  plain,  no  point 
of  which  is  as  much  as  1,000  miles  from  the  sea. 

The  mean  height  of  Europe  is  990  feet,  57  per  cent  of  it  is  below  660  feet, 
and  less  than  2  per  cent  is  above  6,6€X)  feet.  AUhough  it  contains  only 
6.7  per  cent  of  the  land,  favorable  conditions  have  made  it  the  home  of 
one  fourth  of  the  human  race,  and  the  dominant  influence  in  modern 
civilization. 

North  America  is  built  on  the  triangular  plan,  with  its  longest 
side  next  to  the  Pacific,  extending  in  a  double  curve  more  than 
6,000  miles,  and  bordered  by  the  lofty  Cordilleras.  The  con- 
tinental limits  are  extended  far  northward  by  the  half -drowned, 
ragged  land  patches  of  the  Arctic  archipelago,  to  which  is 
attached  the  largest  of  islands,  Greenland.  The  southeastern 
side  is  paralleled  for  about  half  its  length  by  the  low  Appalachian 
highland.  The  southern  extremity  tapers  off  into  the  crooked 
Isthmus  of  Panama,  which  connects  it  with  South  America. 
The  body  of  the  continent  is  made  up  of  the  largest  continuous 
low  plain  in  the  world.  It  resembles  Eurasia  as  the  left  hand 
resembles  the  right,  presenting  to  the  Atlantic  a  low  and  broken 
coast,  penetrated  on  the  south  by  the  Mexican  and  Caribbean 
mediterranean,  on  the  north  by  Hudson  Bay,  and  between  the 
two  by  drowned  river  valleys,  all  of  which  give  access  to  the 
interior  plains. 

Lying  on  the  opposite  side  of  the  north  Atlantic  from  Europe,  and  2,000 
to  3,000  miles  distant,  North  America  has  felt  the  influence  of  European 
civilization  more  strongly  than  any  other  land.  Like  Eurasia,  it  faces 
the  Atlantic  and  presents  to  the  Pacific  a  high  and  forbidding  back.  Its 
average  elevation  is  2,300  feet,  ^;^  per  cent  of  it  is  below  660  feet,  and  6  per 
cent  is  above  6,600  feet.  Its  area  is  16  per  cent  of  the  land,  and  its  popu- 
lation 7.5  per  cent  of  the  inhabitants  of  the  world. 

South  America  is  a  simplified  copy  of  North  America,  re- 
sembHng  it  in  triangular  form  tapering  southward,  and  in  having 
a  high  western  margin,  low  interior  plains,  and  for  the  most  part 
a  low  Atlantic  coast.     It  is  characterized  by  the  smoothness  of 


30  PHYSICAL   GEOGRAPHY 

its  coast  line  and  the  magnitude  of  its  rivers,  of  which  the  Amazon 
is,  in  area  of  basin  and  volume  of  discharge,  the  largest  in  the 
world. 

^  Settlers  have  foun^  it  much  more  difficult  to  penetrate  and  occupy 
than  North  America,  and  its  inhabitants,  still  largely  of  native  Indian 
blood,  are  on  the  whole  much  less  advanced  in  civiUzation.  Its  average 
elevation  is  1,900  feet,  43  per  cent  is  below  660  feet,  and  9  per  cent  is 
above  6,600  feet.  It  contains  11  per  cent  of  the  land,  and  2.4  per  cent 
of  the  people  of  the  world. 

Africa  resembles  the  Americas  in  triangular  outline,  but  is  the 
most  compact  and  unbroken  of  the  continents.  About  70  per 
cent  of  its  surface  is  a  plateau  with  steep  margins.  Although 
its  northern  coasts  are  in  close  touch  with  Eurasia  and  have 
shared  in  its  history  and  civiHzation,  the  great  desert  of  Sahara 
has  been  an  almost  impassable  barrier  to  penetration  from  that 
side.  On  the  east  and  west,  deserts,  dense  forests,  rapids  and 
falls  in  the  rivers,  and  an  unhealthful  climate,  have  combined  to 
prevent  occupation  and  to  retard  progress  in  culture^ 

Its  native  peoples  have  remained  for  thousands  of  years  in  a  condition 
of  savagery  which  justifies  the  name  of  "  the  dark  continent."  Nearly 
every  square  mile  of  it  is  now  under  the  influence  and  partial  control  of 
European  people,  and  its  future  seems  hopeful.  Its  average  elevation  is 
2,130  feet,  15.4  per  cent  is  below  660  feet,  and  2.4  per  cent  is  above  6,600 
feet.  It  contains  20  per  cent  of  the  land  area,  and  8.6  per  cent  of  the 
population  of  the  world. 

Australia,  including  New  Guinea  and  Tasmania,  is  a  simplified 
copy  of  Africa,  with  the  southern  extension  greatly  reduced  in 
size.  Its  surface  is  largely  a  dry  plateau,  with  folded  mountains 
on  the  east  and  north  (in  New  Guinea). 

Isolated  and  cut  off  from  the  great  centers  of  plant  and  animal  life  since 
early  geologic  times,  all  its  indigenous  inhabitants  are  of  a  very  primitive 
type.  On  this  account  they  offered  little  resistance  to  European  colonists, 
who  within  the  last  century  have  taken  complete  possession  of  the  habitable 
parts  of  the  mainland.  Its  average  elevation  is  1,150  feet,  36  per  cent  is 
below  660  feet,  and  less  than  one  per  cent  is  above  6,600  feet.  It  now 
supports,  on  6  per  cent  of  the  land  area,  one  third  of  one  per  cent  of  the 
population  of  the  world. 


THE  PLAN  OF  THE  EARTH  3I 

Antarctica.  —  That  there  is  an  area  of  continental  land  around  the 
south  pole,  about  haK  as  large  again  as  Europe,  seems  now  to  be  definitely 
settled,  but  it  is  so  deeply  buried  in  snow  and  ice  that  its  outlines  and  sur- 
face are  imperfectly  known.  Its  average  elevation  is  twice  as  great  as  that 
of  any  other  continent.  It  is  now  in  the  twentieth  century  becoming  a  field 
for  systematic  exploration.  On  account  of  severity  of  climate  and  difficulty 
of  approach,  sojourn,  and  travel,  the  progress  of  discovery  will  be  slow  and 
costly.  It  contains  no  permanent  human  inhabitants,  and  little  life  of  any 
kind,  except  sea  birds  which  nest  and  breed  upon  its  coasts. 

Islands.  —  Nearly  all  the  large  islands  and  many  small  ones 
stand  upon  the  continental  shelf  and  are  therefore  continental. 
Greenland,  the  Arctic  archipelago,  Newfoundland,  and  the 
Greater  Antilles  belong  to  North  America;  the  British  and 
Mediterranean  islands  to  Europe;  New  Guinea  and  Tasmania 
to  Australia;  Ceylon,  the  Malay  archipelago,  the  Philippines, 
Japan,  Sakhalin,  and  Nova  Zembla  to  Asia.  Madagascar,  New 
Zealand,  Iceland,  and  perhaps  Spitzbergen  and  Franz  Josef 
Land  occupy  detached  portions  of  the  continental  platform. 
The  numerous  small  islands  of  the  Pacific  and  some  in  other 
parts  of  the  sea  are  the  tops  of  submerged  mountain  ranges  or 
volcanic  peaks  which  rise  from  the  deep  sea  floor,  and  are  there- 
fore oceanic. 

Oceanic  islands  are  of  small  area,  isolated  by  wide  stretches  of  deep 
water,  and  have  Httle  variety  of  resources.  Consequently,  they  constitute 
an  environment  unfavorable  for  the  development  of  the  higher  animals, 
including  man.  The  part  which  they  have  played,  or  ever  will  play,  in 
the  Ufe  history  of  the  globe  is  very  small. 

Summary.  —  The  principal  features  of  the  land  relief  of  the 
globe  consist  of  a  nearly  continuous  belt  of  highland  near  the 
shores  of  the  Pacific  and  Indian  oceans,  and  wide  areas  of  low- 
land bordering  the  Atlantic  and  Arctic  oceans.  Consequently 
nearly  all  the  large  rivers  flow  into  the  Atlantic  and  Arctic, 
Asia  only  contributing  streams  of  the  first  class  to  the  Pacific 
and  Indian  drainage.  These  facts  account  for  the  greater  im- 
portance, in  modern  times,  of  the  Atlantic  and  of  the  lands 
bordering  upon  it. 


CHAPTER  III 
WORLD   ECONOMY 

The  earth  is  a  sort  of  organism  of  which  all  the  parts  work 
together  harmoniously  like  those  of  a  plant  or  animal.  No 
part  of  the  earth  is  dead,  but  Hke  a  tree  it  is  most  active  on  the 
outside.  Everything  that  goes  on  in  the  world  is  made  possible 
by  a  multitude  of  conditions  which  probably  do  not  exist  in  the 
same  combination  upon  any  other  planet. 

The  position  of  the  earth  —  its  distance  from  the  sun  —  deter- 
mines the  amount  of  heat  which  it  receives.  This  is  sufficient  to 
maintain  at  all  places  upon  the  face  of  the  earth  a  temperature 
which  never  falls  lower  than  about  1 20  degrees  below  the  freezing 
point  of  water  (—  88°  F.),  and  never  rises  higher  than  about 
120  degrees  above  the  freezing  point  (152°  F.).  This  makes  it 
possible  for  large  quantities  of  water  to  exist  in  each  of  three 
forms  —  solid  ice,  Hquid  water,  and  gaseous  vapor. 

The  form  of  the  earth  determines  the  angle  at  which  the  nearly 
parallel  rays  of  the  sun  strike  its  face  at  different  latitudes,  and 
consequently  the  amount  of  heat  received  per  square  mile.  This 
gives  a  variety  of  temperatures,  ranging  from  the  torrid  to  the 
frigid. 

The  attitude  of  the  earth,  or  the  inchnation  of  its  axis,  in  com- 
bination with  its  daily  and  yearly  motions,  determines  a  change 
of  seasons,  or  variation  of  temperature,  at  all  latitudes,  and 
prevents  both  the  constancy  which  would  exist  if  the  earth's 
axis  were  perpendicular  to  the  plane  of  its  orbit,  and  the  excessive 
variation  which  would  result  if  the  axis  were  nearly  parallel  to 
that  plane. 

The  revolution  of  the  earth  around  the  sun  at  a  nearly  uniform 
speed  in  an  orbit  which  is  nearly  circular  brings  about  the  regular 

32 


WORLD   ECONOMY  33 

succession  of  seasons  and  years,  each  of  which  is  of  moderate 
length.  The  succession  of  warm  and  cool,  or  wet  and  dry, 
seasons  gives  to  plants  and  animals  alternating  periods  of  com- 
parative rest  and  activity. 

The  rotation  of  the  earth  upon  its  axis  exposes  the  greater 
part  of  its  face  to  alternations  of  heat  and  cold,  light  and  dark- 
ness, at  short  intervals,  and  imposes  upon  living  beings  corre- 
spondingly short  and  frequent  periods  of  activity  and  rest.  It 
also  enables  men  to  look  out  at  night  into  space,  see  the  moon 
and  stars,  and  learn  something  of  the  universe  of  which  the 
planet  earth  forms  an  insignificant  part. 

The  structure  of  the  earth  includes  solid,  liquid,  and  gaseous 
spheres.  The  size  and  weight  of  the  solid  sphere  largely  deter- 
mine the  force  of  gravity,  which  is  sufficient  to  prevent  the 
atmosphere  from  escaping  into  space  and  to  give  it  such  com- 
position and  density  as  to  support  plant  and  animal  life.  The 
attraction  of  the  earth  also  determines  the  weight  of  every 
object  upon  its  face,  and  the  strength  or  rigidity  of  plants  and 
the  muscular  power  of  animals  are  nicely  adapted  to  support  or 
to  move  their  own  and  other  weights.  The  earth  crust  gives  a 
firm  support  for  all  creatures  which  live  upon  the  land,  and  to 
plants  soil  for  anchorage  and  a  storehouse  of  available  food. 
The  depressions  in  it  form  basins  which  hold  most  of  the  water 
and  prevent  it  from  covering  the  crust  completely.  Although 
the  form  and  surface  of  the  crust  are  continually  changing,  the 
changes  are  slow,  and  the  crust  is  relatively  the  most  fixed  and 
stable  part  of  the  earth  outside  the  core. 

Circulating  Systems.  —  In  contrast  with  the  rigidity  of  the 
crust,  the  fluid  masses  of  water  and  air  are  very  mobile  and  make 
it  possible  for  extensive  systems  of  currents  to  circulate  in  the 
atmosphere,  in  the  sea,  and  on  the  land. 

The  air  is  seldom,  if  ever,  perfectly  still.  Driven  by  the  heat  of  the 
sun,  it  is  rising,  or  settling,  or  moving  horizontally  in  broad  streams  which 
cover  thousands  of  miles  and  extend  around  the  earth.  The  whole  mass 
is  whirling  in  great  spirals  from  equator  to  poles  and  back  again,  forming 


34  PHYSICAL   GEOGRAPHY 

a  planetary  wind  system,  analogous  to  the  circulation  of  blood  in  animals. 
Driven  by  the  winds,  the  surface  waters  of  the  ocean  are  in  perpetual 
motion,  drifting  around  and  across  the  basins.  The  water  of  the  sea 
evaporates,  mingles  with  the  air,  spreads  over  the  land,  falls  as  rain  or 
snow,  and  runs  back  again  into  the  sea,  completing  a  third  circuit.  The 
land  is  attacked  by  the  air,  worn  away  by  the  water,  and  carried  into  the 
sea.  The  water  penetrates  the  earth  crust  and,  circulating  through  it,  dis- 
solves, deposits,  and  concentrates  metallic  ores  and  other  minerals,  some- 
times bringing  them  to  the  surface  in  mineral  springs  and  geysers.  Thus 
the  earth  has  three  great  circulatory  systems,  active  in  its  solid  as  well  as 
its  fluid  parts,  which  keep  its  materials  in  motion  and  make  its  face  to 
undergo  perpetual  change. 

The  water  supplies  plants  and  animals  with  food  and  also 
with  a  circulating  fluid  which  distributes  new  material  to  their 
tissues  and  brings  away  waste.  The  air  supplies  plants  with 
carbon  which  forms  the  bulk  of  their  food,  and  both  plants  and 
animals  with  oxygen  which  they  breathe  and  by  which  they 
maintain  the  chemical  changes  upon  which  life  depends.  The 
air  penetrates  to  the  bottom  of  the  sea  and  makes  the  whole 
mass  of  water  habitable  by  millions  of  living  forms. 

Solar  Energy.  —  The  sun  shines  down  through  the  atmosphere 
and  into  the  water,  and  its  light,  heat,  and  chemical  rays  furnish 
the  power  or  energy  which  keeps  things  moving  and  alive  upon 
the  face  of  the  earth. 

The  air  and  water  absorb  and  retain  the  heat  of  the  sun,  tempering  its 
intensity  by  day,  preventing  its  too  rapid  escape  by  night,  and  maintaining 
over  nearly  the  whole  face  of  the  earth  such  a  temperature  as  plants  and 
animals  require.  Not  far  below  lies  the  fervent  heat  of  the  interior,  and 
not  far  above,  the  intense  cold  of  stellar  space. 

The  Plan  of  the  earth  presents  a  vast  expanse  of  water  broken 
at  intervals  by  large  and  small  masses  of  land.  While  the  land 
masses  predominate  in  the  northern  hemisphere,  their  longer 
axes  extend  north  and  south  through  so  many  degrees  of  latitude 
as  to  traverse  all  the  zones  of  climate.  This  variety  is  made 
still  greater  by  diversities  of  elevation,  relief,  and  distance  from 
the  sea.  The  number  and  variety  of  living  forms  probably 
decrease  from  near  sea  level  downward  to  the  deep  sea  floor  and 


WORLD  ECONOMY  35 

upward  to  the  mountain  tops,  but  the  great  expanse  of  sea  surface 
and  the  low  average  elevation  of  the  land  make  a  very  large 
proportion  of  the  face  of  the  earth  available  for  a  dense  popula- 
tion of  some  kind.  The  arrangement  and  variety  of  situation, 
relief,  soil,  and  climate  have  brought  about  a  corresponding  variety 
of  living  forms,  each  adapted  to  the  pecuHar  set  of  conditions 
under  which  it  lives.  Probably  no  large  part  of  the  sea  or  land 
is  entirely  devoid  of  Hfe;  but  the  sphere  of  life  is  strictly  confined 
to  the  thin  shell  of  the  earth  where  land,  water,  and  air  inter- 
mingle. 

Human  Life.  —  The  most  important  and  interesting  thing 
about  the  earth  is  the  fact  that  men  live  upon  it.  So  far  as  we 
know  this  is  the  only  human  planet.  Man  was  originally  a  land 
animal,  and  upon  the  land  a  large  majority  of  human  beings  will 
always  Hve.  But  using  the  land  as  a  base,  man  has  extended  his 
field  of  activity  over  the  sea  and  into  the  lower  atmosphere. 

He  requires  a  constant  supply  of  oxygen  from  the  air,  and  a  supply  of 
food  at  short  intervals,  which  he  gets  from  plants,  animals,  and  water.  He 
must  also  maintain  his  body  at  a  constant  temperature,  which  he  does 
by  the  consumption  of  food  on  the  inside  and  the  use  of  clothing,  shelter, 
and  artificial  heat  on  the  outside.  For  clothing,  building  materials,  and 
fuel  he  is  again  dependent  upon  plants,  animals,  and  rocks.  He  could  not 
live  many  minutes  upon  the  moon,  which  has  no  soil,  water,  air,  or  vege- 
tation. From  the  natural  resources  of  the  earth  he  has  learned  to  obtain 
much  more  than  the  bare  necessities  of  life,  which  he  shares  with  other 
animals.  He  has  learned  to  satisfy  his  ever-growing  wants  for  safety, 
comfort,  and  luxury,  and  to  gratify  his  hunger  for  knowledge,  his  taste  for 
beauty,  his  love  of  social  enjoyment,  and  his  longing  for  the  things  which 
he  finds  most  valuable. 

Geography  has  something  to  say  about  all  these  things,  and 
seeks  to  understand  how  they  have  come  to  be  where  and  what 
they  are.  It  studies  the  world  organism  and  tries  to  discover 
how  men  can  live  in  it  and  lead  so  many  different  kinds  of  hfe 
as  they  do  in  different  parts  of  it,  what  natural  conditions  help 
or  hinder  them,  and  how  they  may  use  the  organism  to  better 
advantage  in  the  future. 


CHAPTER   IV 


THE   LAND 

Structure.  —  The  ground  upon  which  we  stand,  walk,  and 
work  is  a  part  of  the  earth  crust,  the  outer  shell  or  layer  of  the 
rock  sphere.     The  crust  contains  hundreds  of  species  of  minerals, 

mixed  together  in  differ- 
'■^'  ■"  '    ent  combinations  to  form 

rocks.  A  large  mass  of 
any  solid  mineral  or  mix- 
ture of  minerals  is  called 
rock.  Almost  everywhere, 
except  upon  very  steep 
slopes,  the  ground  is  com- 
posed of  loose,  incoherent 
material,  commonly  called 
earth  or  soil,  and  distin- 
guished as  clay,  sand, 
gravel,  pebbles,  boulders, 
or  mixtures  of  them. 
They  are  all  fragments  of 
older  rocks  which  have 
been  broken  up  and  de- 
composed. This  sheet  of 
loose,  fragmentary  mate- 
rial may  be  hundreds  of 
feet  thick,  and  is  called  mantle  rock,  because  it  overlies  and  covers 
the  other  rock.  The  upper  foot  or  two  of  mantle  rock  is  gen- 
erally mixed  with  humus,  or  decayed  vegetable  matter,  and  con- 
stitutes the  soil,  in  the  strict,  or  agricultural,  sense  of  the  word. 
Bed  Rock.  —  If  a  boring  is  made   anywhere  down   through 

36 


Fig.  20.  —  Stratified  sand  and  gravel,  Terre  Haute, 
Ind. 


THE  LAND 


37 


the  mantle  rock,  it  will  be  found  to  be  underlain  by  bed  rock, 
a  compact,  coherent  mass,  which  is  not  easily  broken  up  or 
removed.  Bed  rock  often  projects  through  the  cover  of  mantle 
rock  and  is  exposed  to  view  upon  a  hillside,  in  the  face  of  a  clijff, 
or  along  the  bed  and  banks  of  a  stream.  Such  an  exposure  of 
bed  rock  on  the  surface  is  called  an  outcrop.  In  most  places  the 
upper  part  of  the  bed  rock  is  stratified,  that  is,  it  lies  in  distinct 
sheets  or  layers  called  strata  (singular  stratum).    The  common 


Fig.  21.  —  Stratified  bed  and  mantle  rock,  Erie  Coiinty,  N.  Y. 


kinds  of  stratified  bed  rock  are  shale,  sandstone,  conglomerate, 
and  limestone.  They  are  also  called  aqueous  or  sedimentary 
rocks,  because  they  have  been  formed  by  the  accumulation  of 
sediment  in  bodies  of  water. 

In  some  places  immediately  beneath  the  mantle  rock,  and 
everywhere  beneath  the  stratified  bed  rock,  lies  a  mass  of  un- 
stratified  rock,  which  owes  its  form  and  structure  to  cooHng 
from  a  plastic  or  molten  condition. 

Melted  rock  has  risen  from  great  depths  and  has  cooled  in  the  cracks 
and  between  the  layers  of  stratified  rock,  or  has  escaped  to  the  surface  and 
spread  out  over  the  country.     Rocks  which  have  solidified  from  a  molten 


38 


PHYSICAL  GEOGRAPHY 


Fig.  22.  — Unstratified  igneous  rock,  Hoboken,  N.  J. 

State  are  called  igneous.  Lava,  of  which  there  are  many  varieties,  is  a  com- 
mon form  of  igneous  rock.  Some  rocks  which  were  originally  sedimentary, 
have  been  changed  by  heat  and  pressure,  but  have  not  been  melted,  and 


Fig.  23.  — Contorted  gneiss,  a  metamorphic  rock,  near  Hudson  Bay.     (Can.  Geol.  Surv.) 


are  called  metamorphic  or  altered  rocks.  Igneous  and  metamorphic  rocks 
are  often  distinguished  as  crystalline,  because  they  are  mainly  or  wholly 
composed  of  crystals,  which  are  often  conspicuous  from  their  shape,  color, 
and  sparkling  luster.     Granite  is  a  good  example  of  crystalline  rock. 


THF   LAND 


39 


Economic  Relations.  —  The  surface,  soil,  vegetation,  and  value 
of  a  region  depend  largely  upon  the  kind  of  rock  which  underUes 
it.  The  common  kinds  of  both  mantle  and  bed  rock  are  dug  or 
quarried  for  use  in  constructing  roads,  streets,  bridges,  houses, 
and  public  buildings,  while  the  finer  kinds,  like  marble  and 
granite,  furnish  beautiful  material  for  buildings,  monuments, 
and  statues.  All  the  useful  minerals,  such  as  coal  and  the  ores 
of  the  metals,  are  obtained  from  the  earth  crust,  generally  from 
the  bed  rock  by  mining.  Thus  the  agricultural  and  mineral 
wealth  of  a  country  depends  upon  the  structure  of  the  earth 
crust. 

Relief  Maps.  —  Many  devices  are  in  use  for  showing  elevation 
and  form,  or  relief,  upon  a  map.  One  of  the  most  common 
and  generally  useful  is  by  "  overlaying  "  with  different  colors 
to  show  successive  stages  of  height  and  depth,  as  on  the  map, 
Fig.  1 6.  Such  a  map  shows  general  elevation  within  certain 
limits,  but  fails  to  show  the  details  of  form.  Each  boundary 
line  of  a  color  or  shade  is  level,  or  everywhere  at  the  same  dis- 
tance, 990  feet,  3,300  feet,  etc.,  above  or  below  sea  level,  measured 
vertically.  These  lines  of  equal  elevation  upon  a  map  are  called 
contour  lines,  or  simply  contours.  By  drawing  contours  at  small 
intervals  relief  may  be  shown  with  any  desired  degree  of  pre- 
cision, and  colors  become  unnecessary. 

The  United  States  Geological  Survey  is  making  a  topographic  atlas  of  the 
United  States,  of  which  about  one  third  is  now  completed.  The  contoured 
maps  in  this  book,  Figs.  28,  30,  31,  35,  etc.,  are  taken  from  it.  They  show 
the  relief,  drainage,  and  culture  or  human  features,  such  as  towns,  houses, 
and  roads,  with  great  detail  and  precision.  It  is  worth  while  to  learn  to  use 
these  maps,  which  are  among  the  best  made  of  any  country  in  the  world. 

Fig.  24  shows  a  sketch  or  picture  of  a  landscape,  and  Fig.  25  a  contoured 
map  of  the  same  region.  In  the  foreground  is  a  portion  of  the  sea,  the 
shore  line  of  which  forms  the  basal  or  zero  contour.  Contours  are  drawn 
upon  the  map  at  intervals  of  fifty  feet  measured  vertically  from  the  sea  level, 
and  they  mark  the  Hues  where  the  seashore  would  be  if  the  sea  should  rise 
fifty,  one  hundred,  etc.,  feet.  Where  the  slope  is  steep,  one  would  have  to 
travel  only  a  short  distance  to  rise  fifty  feet;  hence  the  contours  are  close 
together.     Where  the  slope  is  gentle,  one  would  have  to  travel  far  to  rise 


40 


PHYSICAL   GEOGRAPHY 


fifty  feet;  hence  the  contours  are  farther  apart.  By  shortening  the  con- 
tour interval  to  ten  or  five  feet^  as  may  be  done  upon  a  large-scale  map, 
the  elevation  of  every  point  may  be  shown  very  precisely.     For  showing 


Fig.  24. 


Fig.  25. 


exact  elevation  no  device  is  equal  to  the  contoured  map;  but  it  has  the 
disadvantage  of  not  being  graphic,  that  is,  of  not  being  understood  by 
everybody  at  a  glance. 

A  very  common  device  for  showing  rehef  upon  a  map  is  the  use  of 
hachures,  or  fine  lines  running  up  and  down  the  slopes,  and  so  drawn  as  to 
show  the  steepness  of  the  slope  by  the  depth  of  shading.  Hachured  maps 
may  be  made  very  graphic  and  almost  equal  to  a  picture.  Figs.  26  and  27 
show  the  relation  between  contoured  and  hachured  maps  of  the  same  area. 
A  combination  of  the  two  is  the  best  possible  method  of  showing  relief  upon 
a  map. 


THE   LAND 


41 


Fig.  26.  —  Contoured  map. 


Fig.  2  7-  — Hachured  map. 


Land  Forms.  —  The  surface  of  the  land  presents  a  variety  of 
forms  which  differ  widely  in  outhne,  elevation,  slope,  mass,  and 
structure.  The  inequalities  of  surface  found  in  any  region  con- 
stitute its  vertical  relief.  A  smooth,  level  plain  might  be  said 
to  have  in  itself  no  relief,  but  if  it  stands  at  a  higher  level 
than  some  adjoining  land  or  water  surface,  it  would  have  relief 
in  relation  to  the  lower  surface. 

The  design  upon  a  coin  stands  out  in  relief  above  the  general  surface  of 
the  metal.  If  the  elevations  are  low  and  the  depressions  shallow,  the  sur- 
face has  low  relief;  if  the  elevations  are  high  and  the  depressions  deep,  the 
surface  has  high  or  strong  relief.  In  common  speech  the  roughness  of  the 
country  means  about  the  same  as  relief. 

The  large  and  controlling  features  of  land  relief  are  plains, 
plateaus,  mountains,  hills,  and  valleys.  The  internal  forces  of 
the  earth  have  raised  some  portions  of  the  land  and  depressed 
other  portions,  producing  plains,  plateaus,  and  mountains  which 
mark  the  main  features  of  the  design.  External  forces,  acting 
chiefly  through  air  and  water,  have  roughened  a  large  part  of 
the  surface  into  an  intricate  pattern  of  smaller  features,  including 
ridges,  valleys,  hills,  hollows,  mesas,  and  basins. 

Plains.  —  Plains,  or  lowlands,  are  broad,  smooth,  gently 
sloping  tracts  of  land  not  far  above  sea  level.  The  borders  of  a 
plain  may  be  sharply  defined  by  the  abrupt  slopes  of  a  mountain 


Fig.  28.  —  Coastal  plain,  drowned  valley,  barrier  beach,  and  lagoon,  New  Jersey. 

42 


Scale  about  i  mile  per  inch.     Contour  interval  lo  feet.     (Barnegat  Sheet,  U.S.G.S.) 

43 


44  PH\^SICAL   GEOGRAPHY 

range,  or  they  may  rise  by  an  almost  imperceptible  grade  to  the 
height  of  a  plateau,  or  slope  gently  to  and  beneath  the  waters 
of  the  sea.  Plains  are  generally  overspread  with  a  deep  layer  of 
mantle  rock  brought  down  from  higher  land  by  streams,  glaciers, 
and  winds,  or  produced  by  the  decay  of  the  bed  rock  underneath. 
Structural  Plains.  —  The  flatness  of  the  great  low  plains  of 
the  world  is  due  to  various  causes.  Most  plains  are  underlain 
by  sedimentary  rocks,  the  strata  of  which  have  not  been  much 
disturbed  from  their  originally  horizontal  position.  The  surface 
is  flat  because  the  strata  beneath  it  lie  flat.  When  the  surface 
thus  conforms  to  the  structure  of  the  earth  crust,  the  plain  is 
called  structural.     It  is  like  the  cover  of  a  closed  book  (Fig.  36). 

The  best  examples  of  the  structural  plain  are  found  in  the  lowlands  which 
border  the  coasts  of  the  continents,  and  are  called  coastal  plains  (Fig.  28). 
They  are  generally  narrow,  but  sometimes,  as  in  the  case  of  the  plains 
along  the  Atlantic  and  Gulf  coasts  of  the  United  States,  they  stretch  back 
hundreds  of  miles  to  the  plateau  or  mountains  which  lie  behind  them. 
Coastal  plains  are  formed  by  the  slow  rising  of  the  sea  bottom  until  it 
emerges  from  the  water.  They  are  covered  with  layers  of  imperfectly  con- 
solidated sediment  which  has  been  brought  down  in  previous  ages  from 
older  lands  and  deposited  offshore.  They  are  continuous  with  the  sub- 
merged plain  of  the  continental  shelf.  They  are  usually  the  latest  addi- 
tions to  the  continent  and  are  composed  of  materials  recently  deposited; 
hence  such  lands  are  young  in  every  sense.  Old  coastal  plains  sometimes 
occur  in  the  interior  of  the  continents,  far  from  the  sea.  They  were  formed 
in  the  same  way  as  the  others,  along  the  shore  of  a  sea  which  has  long 
since  disappeared,  and  are  now  far  inland  because  other  plains  and  even 
mountains  have  risen  between  them  and  the  present  coast  line.  A  strip 
of  country  extending  from  Wisconsin  to  New  York  along  the  south  side  of 
the  Great  Lakes  is  an  old  coastal  plain.  The  most  extensive  plains  in  the 
world  occur  in  the  interior  of  continents,  as  in  North  America,  South 
America,  and  Eurasia.  These  are  for  the  most  part  structural  plains, 
underlain  by  nearly  horizontal  strata. 

Worn-down  Plains.  —  Some  large  plains  owe  their  flatness 
and  low  elevation  to  erosion.  Once  high  and  rough,  they  have 
been  worn  down  by  weathering  and  the  work  of  streams  and 
glaciers  to  a  nearly  even  surface  not  far  above  sea  level.     Such 


THE  LAND  45 

plains  are  seldom  as  smooth  as  coastal  plains,  but  are  studded 
with  low,  rounded  hills,  composed  of  materials  less  easily  eroded 
than  the  rest.  They  are  called  worn-down  plains,  peneplains, 
or  plains  of  degradation  (Figs.  29,  30). 

A  large  U-shaped  area  surrounding  Hudson  Bay,  from  Labrador  to  the 
Arctic  Ocean,  was  once  occupied  by  a  mountain  range  which  has  been 
worn  down  to  its  very  roots.  It  is  composed  largely  of  igneous  and  met- 
amorphic  rocks  which  must  have  been  formed  originally  far  below  the 


Fig.  29.  —  Stereogram  of  a  worn-down  plain. 
Complex  structure  shown  in  section  on  the  edges. 

surface,  and  have  been  exposed  by  the  removal  of  the  rocks  which  once 
covered  them  (Figs.  23,  in).  The  structure  is  complex,  that  is,  masses  of 
different  kinds  of  rock  lie  mingled  together  in  almost  every  possible  shape 
and  position,  and  the  present  surface  cuts  across  them  without  any  con- 
formity to  their  shapes  and  positions.  This  region  is  called  the  Laurentian 
peneplain.  A  similar  plain  in  northern  Europe  occupies  Finland,  Lapland, 
and  Sweden.  Such  plains  are  among  the  oldest  lands  on  the  globe,  because 
it  has  required  millions  of  years  to  wear  them  down  to  their  present  form 
and  height. 

Alluvial  Plains.  —  Many  plains,  usually  of  less  extent  than 
those  already  described,  have  been  formed  by  the  spreading  out 
of  sheets  of  mantle  rock  over  a  surface  previously  more  or  less 


Fig.  30. — Wom-down  plain,  Georgia  and  South  Carolina.    Scale  about  2  miles  per  inch. 

Contour  interval  50  feet.     (Crawfordville  Sheet,  U.S.G.S.) 

46 


Fig.  31.  — Alluvial  plain,  Wabash  River,  Indiana  and  Illinois.     Scale  about  2  miles  per  inch. 
Contour  interval  20  feet.     (Patoka  Sheet,  U.S.G.S.) 

47 


48 


PHYSICAL   GEOGRAPHY 


Fig.  32.  — Alluvial  plain,  Wabash  River,  near  Terre  Haute,  Ind. 

uneven.  A  large  river,  more  or  less  along  its  whole  course,  but 
especially  toward  its  mouth,  gets  out  of  its  banks  in  times  of 
high  water,  spreads  over  the  adjoining  country,  and  deposits  a 
coat  of  mud  or  sand,  thus  building  up  a  smooth  surface  known 


Fig.  33.  — Lake  plain,  Clearwater,  Minn.    Outlet  in  the  distance. 


THE   LAND 


49 


as  a,  flood  plain  (Figs.  31,  32,  75,  76).  When  it  enters  the  sea  all 
its  remaining  load  of  sediment  is  dropped  and  the  flood  plain 
is  built  out  into  the  water,  forming  a  delta  (Fig.  69).  Plains 
thus  made  by  the  accumulation  of  river  sediment  are  called 
alluvial.  The  alluvial  plains  of  the  Mississippi,  Amazon,  Ganges, 
Nile,  and  Hoang  are  among  the  largest  in  the  world. 

Lake  Plains.  —  All  streams  which  flow  into  a  lake  carry  and  deposit 
sediment  until  in  time  the  lake  basin  may  be  filled  up  and  converted  into 
an  almost  perfectly  level  lake  plain  or  lacustrine  plain  (Fig.  ss)-  The  famous 
wheat-growing  district  of  Minnesota,  North  Dakota,  and  Manitoba  is  the 
bed  of  an  old  glacial  lake. 

Glacial  Plains.  —  In  North  America  and  Europe  milHons  of 
square  miles  have  been  covered  by  moving  ice  sheets,  which,  as 


Fig.  34.  —  Glacial  plain,  Laporte  County,  Ind. 


they  melted,  deposited  vast  sheets  of  mantle  rock  called  glacial 
drift,  of  such  thickness  as  to  fill  up,  bury,  and  smooth  over  the 
irregularities  of  the  bed-rock  surface.  The  nearly  level  surface 
thus  produced  is  called  a  glacial  plain  (Figs.  34,  35). 

Alluvial,  glacial,  and  lacustrine  plains  may  be  grouped  together 
as  plains  of  accumulation  or  aggradation. 

Eolian  Plains.  —  In  regions  of  small  rainfall  and  scant  vege- 
tation the  loose  mantle  rock  is  Hfted  and  drifted  about  by  the 
winds,  and  some  of  it  is  carried  entirely  out  of  the  region  and 


Fig.  3S.  —  Glacial  plain  and  cliff  coast,  Illinois.     Scale  about  i  mile  per  inch. 
Contour  interval  lo  feet.     (Highwood  Sheet,  U.S.G.S.) 

50 


Fig.  36.  —  Portion  of  the  High  Plains,  Colorado.     Scale  about  2  miles  per  inch.     Contour 
interval  25  feet.     Irrigation  canal  near  4000  foot  contour.     (Las  Animas  Sheet,  U.S.G.S.) 

51 


52 


PHYSICAL   GEOGRAPHY 


deposited  over  neighboring  lands  or  in  the  sea.  This  process, 
long  continued,  produces  a  worn-down  plain,  studded  with  knobs 
of  resistant  rock,  and  its  level  may  be  degraded  even  below  that 
of  the  sea. 

The  Kalahari  desert  in  South  Africa  owes  its  relief  to  this  cause,  and 
may  be  called  a  wind-worn  plain.  The  material  carried  away  from  a 
wind-worn  plain  may  accumulate  upon  neighboring  lands  in  such  quan- 


Fig.  37.  — 'VSIlnd-worn  plain,  Algerian  Sahara. 


tities  as  to  bury  them  hundreds  of  feet  deep  under  a  mantle  of  fine  dust. 
In  China  thousands  of  square  miles  are  covered  with  a  material  called 
loess,  which  has  been  blown  from  the  dry  plateaus  of  central  Asia.  Both 
the  wind- worn  plains  and  those  made  by  the  deposition  of  wind-blown  dust 
are  called  eolian  plains  (Figs.  37,  141,  142). 

Economic  Relations.  —  On  account  of  their  accessibility,  fer- 
tility, and  mild  climate,  plains  have  ever  been  the  most  densely 
populated  parts  of  the  earth.  It  is  probable  that  75  per  cent 
of  the  human  race  hve  less  than  1,000  feet  above  the  sea.  The 
wealthiest  and  most  highly  civilized  peoples  of  the  world  live 
on  the  plains,  and  there  nearly  all  the  great  cities  have  sprung 


THE  LAND 


S3 


up.     The  most  favored  countries  are  those  which  possess  broad 
plains  traversed  by  great  rivers  and  bordering  upon  the  sea. 

Alluvial,  glacial,  and  lacustrine  plains,  on  accoun  of  depth  and  fertility 
of  soU,  are  the  best  agricultural  regions  in  the  world.  Coastal  plains  are 
usually  less  productive.  Worn-down  plains  are  often  infertile  on  account 
of  lack  of  soil,  but  they  sometimes  support  forests  which  yield  valuable 
timber  and  swarm  with  fur-bearing  animals,  as  in  the  Laurentian  region  of 
Canada.  They  are  apt  to  be  rich  in  mineral  wealth,  because  long-con- 
tinued erosion  has  laid  bare  veins  of  ore  once  deeply  buried.  The  iron  and 
copper  mines  of  the  Lake  Superior  region,  the  silver,  cobalt,  and  nickel 
mines  north  of  Lake  Huron,  and  the  diamond  deposits  of  South  Africa 
occur  in  worn-down  plains.  EoHan  plains  are  generally  deserts,  not  on 
account  of  poor  soil,  but  because  they  occur  only  in  regions  where  the  rain- 
fall is  very  scanty. 

Plateaus.  —  Plateaus  are  broad  masses  of  elevated  land. 
They  are  high  plains,  and  there  is  no  fixed  and  definite  line  of 
demarcation  between 


plains  and  plateaus. 
It  is  sometimes  con- 
venient to  use  660  feet 
(200  meters),  1,000 
feet,  or  even  2,000  feet 
above  the  sea  to  Hmit 
the  height  of  plains. 

In  a  region  of  low 
relief,  a  broad,  massive 
elevation  above  1,000  feet 
may  be  called  a  plateau, 
while  in  a  region  of  high 
relief  the  name  would  be 

given  only  to  a  similar  area  above  2,000  feet.  Plateaus  may  be  as  smooth 
and  level  as  plains,  as  in  the  case  of  the  High  Plains  eas-t  of  the  Rocky 
Mountains,  but  are  generally  more  broken  (Figs.  36,  2>^) .  They  are  often 
bordered  or  traversed  by  mountain  ranges.  Low  plateaus  may  be  called 
uplands,  and  high  plateaus  highlands. 

Economic  Relations.  —  On  account  of  rougher  surface,  poorer 
soil,  and  colder  and  drier  climate,  plateaus  are  generally  less 


Fig.  38. — A  plateau:  Mesa  Verde,  Colorado. 


54 


PHYSICAL   GEOGRAPHY 


favorable  for  human  occupation  than  plains.  In  middle  lati- 
tudes, plateaus  of  moderate  height,  such  as  the  High  Plains  of  the 
United  States,  and  some  of  the  plateaus  of  central  Asia,  consti- 
tute a  region  of  steppes,  covered  with  patches  of  grass,  over  which 
the  people  wander  with  their  herds  of  horses,  cattle,  and  sheep 
in  search  of  pasture.  Very  high  plateaus,  such  as  Tibet,  have 
an  Arctic  climate,  and  are  almost  uninhabitable.  In  tropical 
regions,  plateaus  such  as  those  of  Mexico,  Peru,  the  Dekkan, 
and  central  Africa  have  a  temperate  climate,  and  are  better 
homes  for  men  than  the  hot  and  unhealthful  plains  which 
border  them. 

Mountains.  —  Mountain  ranges  are  long,  narrow  ridges  of 
great  height.  They  are  usually  due  to  the  folding,  crumpling, 
and  breaking  of  the  earth  crust  along  Hnes  of  weakness  (Figs.  39, 


Fig,  39.  —  Fold  in  the  Jura  Mountains. 


41,  and  frontispiece).  They  are  characterized  by  complex 
structure,  steep  slopes,  and  sharp  crests.  The  crest  is  cut  by 
notches,  or  passes,  into  a  series  of  peaks,  which  from  a  distance 
look  hke  the  teeth  of  a  saw.  The  notches  seldom  extend  halfway 
down  to  the  base.  Mountain  ranges  seldom  occur  singly,  but 
usually  many  ranges  extending  in  the  same  general  direction 
form  a  mountain  system.  All  mountains  owe  their  height  to  up- 
heaval of  the  earth  crust  by  internal  forces,  but  their  forms  are 
due  chiefly  to  erosion  (Figs.  40,  44,  58,  60,  102,  103,  104,  105, 
106,  109). 


wmmmm^nmmm^ 


Fig.  40.  —  A  portion  of  the  Sierra  Nevada,  with  glacial  cirques  and  lakes,  California. 

Scale  about  2  miles  per  inch.     Contour  interval  100  feet.     (Mt.  Whitney  Sheet,  U.S.G.S.) 

55 


&-.r''  -.      -  .    .  -  , 

^'  ^ 

JS^ 

^^^^ 

Mil 

W^"  '^^^^^ 

&" .  ^ 

■^Pypl^^^^'lE^SStPiKBRSjMBEJ^^^P^     -*" 

^P^ 

Fig.  41.  —Folded  rocks,  Turkestan. 


Fig.  42.  —Dissected  plateau,  Toe  River,  North  Carolina. 
S6 


Fig.  43.  —  Dissected  plateau  and  cliff  coast,  California.     Scale  about  i  mile  per  inch. 
Contour  interval  25  feet.     (San  Mateo  Sheet,  U.S.G.S.) 

57 


58  PHYSICAL   GEOGRAPHY 

Plateaus  are  sometimes  dissected  by  a  network  of  valleys  into  a  system 
of  sharp  ridges  and  peaks  which  resemble  in  form  "  a  sea  of  mountains," 
and  are  not  improperly  called  mountains,  although  dissected  plateau  would 
be  a  more  exact  descriptive  name  (Figs.  42,  43,  73).  The  elevations  left 
on  worn-down  plains  or  plateaus,  projecting  Hke  nail  heads  or  knots  in  an 
old  floor,  may  be  of  mountainous  size,  Hke  the  White  Mountains  of  New 
Plampshire.  Isolated  mountains  or  peaks,  not  forming  a  part  of  a  range, 
are  always  remnants  left  by  erosion,  or  of  volcanic  origin.  Some  of  the 
most  famous  mountains  of  the  world  belong  to  the  latter  class,  as  Vesuvius 
and  Etna  in  Europe  and  KiUmanjaro  and  Kenia  in  Africa  (Figs.  51,  52, 
53,  54). 

Economic  Relations.  —  Mountains  are  difficult  to  penetrate, 
to  cross,  or  to  live  on.  They  are  formidable  barriers  to  the 
migration  of  plants,  animals,  and  men,  and  the  inhabitants  upon 
opposite  sides  of  a  mountain  range  are  often  very  unlike.  The 
vertical  height  and  steepness  of  mountains  render  travel  and 
transportation  among  them  costly  in  effort  and  limited  in  amount. 
The  use  of  vehicles  is  often  impossible,  and  neither  man  nor 
beast  can  climb  up  and  down  with  a  heavy  load.  The  soil  upon 
mountain  slopes  is  thin  and  poor,  and  there  are  large  areas  of 
bare  rock.  The  climate  of  mountains  is  severe  in  proportion  to 
their  height,  and  the  higher  summits  are  covered  with  snow  and 
ice.  Agriculture  is  impossible  except  in  the  valleys.  Moun- 
tains act  as  condensers  of  water  vapor  and  have  a  heavier  rainfall 
than  the  adjacent  lowlands.  Most  mountains  are  forested  up  to 
a  certain  height  called  the  timber  line.  Where  the  forests  have 
been  burned  or  cut  grasses  flourish.  Hence  mountaineers  are 
usually  lumbermen  or  herdsmen.  The  upheaval  of  a  mountain 
range  breaks  up  the  earth  crust  and  produces  many  cracks  in 
which  the  ores  of  metals  may  be  deposited  by  deeply  circulating 
waters.  The  rapid  erosion  of  mountains  removes  the  cover  and 
exposes  the  veins  of  ore  upon  the  surface.  Therefore  many  of 
the  richest  mines  of  gold,  silver,  copper,  lead,  and  other  minerals 
occur  in  mountainous  regions.  The  permanent  population  of 
mountains  is  sparse.  The  people  are  rude,  hardy,  and  thrifty, 
because  only  such  can  make  a  living  there,  and  luxuries  are  few. 


THE  LAND  59 

They  are  free  and  liberty-loving  because  they  can  easily  defend 
themselves  against  invaders.  Conquered  peoples  may  take  refuge 
in  the  mountains,  leaving  the  lowlands  to  be  occupied  by  their 
more  numerous  conquerors-.  Towns  and  cities,  such  as  Leadville 
and  Cripple  Creek  in  Colorado,  sometimes  spring  up  around  a 
rich  mine  above  the  timber  line,  but  the  citizens  are  dependent 
upon  the  lowlands  for  everything  they  use.  Mountain  scenery  is 
grand  and  picturesque,  and  the  air  is  pure,  invigorating,  and  in 
summer  agreeable.  Hence  mountains  are  pleasure  and  health 
resorts  for  the  people  of  the  lowlands. 

The  Alps  have  become  the  playground  of  Europe,  and  are  visited  by 
about  a  million  people  every  season.  Railroads,  coach  roads  (Fig.  295), 
and  hotels  are  constructed  for  their  accommodation,  and  the  inhabitants 
reap  a  rich  harvest  from  their  guests. 

Mountain  streams  have  a  rapid  fall  and  constant  volume  which  make 
them  especially  valuable  for  water  power.  As  coal  becomes  more  scarce 
and  costly,  manufacturers  will  seek  water  power  to  run  their  machinery, 
and  mountainous  countries,  such  as  Switzerland,  Italy,  and  Norway,  may 
become  great  manufacturing  countries. 

Mountains  are  great  soU  factories,  where  bed  rock  is  rapidly  broken  up 
and  carried  away  by  streams  to  be  deposited  in  their  lower  valleys.  The 
rich  and  populous  plains  of  the  Po,  the  Rhone,  the  Rhine,  and  the  Danube 
have  been  built  up  by  the  waste  of  the  Alps.  The  soil  of  the  alluvial  plains 
of  the  Mississippi,  the  Amazon,  the  Ganges,  and  the  Hoang  has  been  brought 
from  the  mountains  in  which  these  rivers  have  their  sources. 

Hills.  —  Hills  are  small  elevations,  and  the  distinction  be- 
tween hills  and  mountains  is  indefinite.  In  a  region  of  moderate 
rehef,  like  Pennsylvania,  ridges  1,000  feet  high  are  called  moun- 
tains, while  in  a  region  of  great  rehef,  like  Colorado,  ridges 
2,000  feet  high  are  called  hills. 

While  all  great  mountain  ranges  owe  their  origin  to  disturb- 
ance and  upheaval  of  the  earth  crust,  most  hills  are  due  either 
to.  the  cutting  out  of  the  valleys  between  them,  or  to  the  heap- 
ing up  of  mantle  rock  by  glaciers,  ice  sheets,  and  winds. 
Hence  hills  are  of  two  classes,  —  hills  of  erosion  and  hills  of 
accumulation. 


f^r^  ^ 


Fig.  45> — Hills  of  accumxilation,  with  basins,  Wisconsin.    Scale  about  i  mile  per  inch. 

Contour  interval  20  feet.     (St.  Croix  Dalles  Sheet,  U.S.G.S.) 

61 


62 


PHYSICAL   GEOGRAPHY 


Fig.  46.  —  Hills  of  erosion:  Jacalitos  Hills,  California.    (U .S.G.S.) 


Fig.  47.  —  Hills  and  hollows  of  glacial  accumulation,  Victor,  N.  Y. 

Hills  vary  in  value  according  to  their  structure,  size,  and  ruggedness. 
Sand  hills  are  generally  worthless,  and  if  mnd-drifted  are  destructive. 
Glacial  hills  may  be  as  productive  as  plains,  although  less  easy  to  culti- 
vate. Some  hills  are  forested,  and  some  furnish  good  pasturage.  A  hilly 
country  is  always  picturesque  and  attractive  for  its  beauty.  It  presents 
a  pleasing  variety  of  slope  and  situation  in  contrast  with  the  monotonous 
sameness  of  the  plains. 

Valleys.  —  Any  depression  between  higher  land  on  each  side 
may  be  called  a  valley.  Wherever  parallel  mountain  ranges  are 
upheaved,  the  corresponding  depression  between  them  is  called 
an  intermont  valley.     The  Valley  of  California  is  an  intermont 


THE  LAND 


63 


Fig.  48.  —  Kettlehole  basins,  Naples,  N.  Y. 

valley  between  the  Sierra  Nevada  on  the  east  and  the  Coast 
Ranges  on  the  west.  Most  valleys  are  long  and  narrow,  but 
between  hills  and  upon  plains  and  plateaus  there  are  many  broad 
depressions,  often  occu- 
pied by  lakes,  which 
should  be  called  hollows 
or  basins. 

Valleys  are  the  most  com- 
mon of  all  relief  forms,  and 
most  of  them  have  been 
made  wholly  or  partly  by 
running  water.  That  is  a 
long  story  which  will  be  told 
in  some  of  the  following 
chapters. 

Broken  Block  Lands. 

—  Some  regions  resem- 
ble in  relief  a  poorly  laid 
pavement  in  which  some 
of  the  bricks  or  tiles 
stand  above  or  below  the 
others.  The  earth  crust 
has  been  broken  by 
nearly  vertical  cracks  into  blocks  which  have  been  displaced, 
some  upward  and  some  downward,  or  tilted  to  one  side.  The 
cracks  are  called  faults,  and  the  process  of  displacement  is 
faulting.     The  elevated  blocks  may  form  steep-sided  table-lands, 


Fig.  49.  —  Faults. 

Block  between  faults  has  dropped  down. 


64 


PHYSICAL   GEOGRAPHY 


or,  if  tilted,  sharp-crested  ridges.     The  depressed  blocks  may 
form  basins  or  rift  valleys,  according  to  their  shape. 

An  area  in  Europe  extending  from  central  France  to  Hungary  has  been 
broken  into  many  pieces,  and  fauLed  into  a  complex  set  of  tables,  ridges, 
and  basins.  The  Mediterranean  region  is  faulted  on  a  very  large  scale. 
The  Sierra  Nevada  of  California  is  a  faulted  block,  the  eastern  edge  of 
which  has  been  tilted  up  to  form  a  very  steep  slope.  Many  of  the  moun- 
tain ranges  of  the  Great  Basin  are  tilted  blocks. 


f  f    f  f 

Fig.  50.  —  Cross  section  of  rift  valley. 

The  subsidence  of  a  long,  narrow  block  between  two  parallel  faults 
produces  a  rift  valley,  of  which  the  valley  of  the  Rhine  from  Basel  to  Bing- 
en  is  a  good  example.  A  rift  valley  on  a  grand  scale  extends  from  lakes 
Nyassa  and  Tanganyika,  in  Africa,  through  the  Red  Sea  to  the  valley  of 
the  Dead  Sea  and  the  Jordan  River  in  Asia,  a  distance  of  about  4,000  miles 
(Fig,  118). 

Volcanic  Lands.  —  Cracks  in  the  earth  crust  often  permit  the 
escape  of  melted  rock,  steam,  and  hot  gases  from  the  interior. 
When  this  takes  place  with  violent  explosions  and  a  brilliant 
display  of  fireworks  the  event  is  a  volcanic  eruption.  Enormous 
quantities  of  lava  (melted  rock)  in  the  form  of  dust,  sand,  and 
cinders  are  thrown  into  the  air  and  spread  over  the  surrounding 
country.  Streams  of  liquid  lava  flow  from  the  vent  and,  grad- 
ually cooling  and  stiffening,  help  to  build  up  a  volcanic  cone  or 
mountain  to  a  height,  in  some  cases,  of  three  or  four  miles.  The 
vent  of  a  volcano  is  called  a  pipe  or  chimney,  and  there  is, 
usually,  a  cup-shaped  depression,  or  crater,  at  the  top.  The 
immediate  cause  of  an  eruption  is  the  sudden  expansion  of 
water  in  the  lava  into  steam.  The  melted  rock  comes  from 
great  depths  and  its  origin  is  not  fully  understood.  Volcanic 
eruptions  produce  a  peculiar  relief  characterized  by  conical  or 
domed  elevations,  standing  singly  or  in  groups  and  lines  and 


Fig.  51.  —  A  volcanic  cone:  Mt.  Shasta,  California.    Scale  about  4  miles  per  inch.    Contour 
interval  joo  feet.     (Shasta  Sheet,  U.S.G.S.) 

65 


66 


PHYSICAL  GEOGRAPHY 


Fig.  S2.  —  Volcano,  New  Guinea. 

varying  in  height  from  a  few  hundred  to  many  thousand  feet 

(Fig.  53). 

Most  of  the  numerous  oceanic  islands  have  been  built  up  by  volcanic 
eruptions  in  the  bottom  of  the  sea,  and  stand  in  lines  along  the  course  of 
submarine   fissures.    In  India  and  in  the  states  of  Oregon,  Idaho,  and 


Fig- 53- 


Volcanic  domes:  Puys  of  central 
France. 


Fig.  54.  —  Sundance  Mountain,  W 
A  dome  of  igneous  rock. 


Washington,  lava  has  flowed  quietly  from  cracks  and  flooded  hundreds  of 
thousands  of  square  miles  to  the  depth  of  several  thousand  feet,  building 
up  a  lava  plateau  with  a  smooth   surface   resembling  that  of   the  sea 

(Fig.  57)^ 


THE  LAND 


67 


Economic  Relations.  —  Volcanic  eruptions  are  temporarily 
destructive  to  life  and  property.  In  1902  an  eruption  of  Mont 
Pelee  in  the  island  of  Martinique,  one  of  the  West  Indies,  utterly 
destroyed  St.  Pierre,  a  city  of  30,000  people,  with  its  inhabitants, 
in  a  few  minutes.  Yet  volcanic  action  is  on  the  whole  construc- 
tive rather  than  destructive.  Vast  quantities  of  water  vapor 
and  carbon  dioxide  are  added  to  the  atmosphere,  and  new  supplies 
of  rock  material  are  transferred  from  the  interior  to  the  exterior 
of  the  earth.  Volcanic  dust  (so-called  ashes)  is  carried  by  the 
wind  hundreds  of  miles  and  sown  broadcast  over  the  land,  renew- 
ing the  soil.  Even  lava  beds,  in  the  course  of  time,  weather 
and  crumble  into  rich  earth  and  become  available  for  the  support 
of  plant  and  animal  hfe.  By  the  agency  of  submarine  volcanoes 
new  lands  are  created  amid  the  waste  of  waters. 


Fig.  55.  —  Results  of  an  earthquake  in  Japan. 


Earthquakes.  —  Broken  block  and  volcanic  lands  are  espe- 
cially subject  to  earthquakes.  Volcanic  eruptions  often  cause 
earthquakes  which  are  locally  violent,  but  affect  only  a  small 


THE  LAND  69' 

area.  Great  disturbances  which  shake  literally  the  whole  earth 
are  incidents  In  the  process  of  faulting,  and  are  due  to  the  sudden 
slipping  of  the  blocks  a'.ong  a  crack  in  the  earth  crust.  The 
movement  of  the  blocks  may  be  vertical  or  horizontal,  and  does 
not  exceed  a  few  feet.  The  jar  travels  through  and  around  the 
earth  in  every  direction,  diminishing  in  intensity  as  the  distance 
from  the  center  of  disturbance  increases. 

Economic  Relations.  —  Near  the  center  an  earthquake  is  often 
exceedingly  destructive  to  property  and  human  life.  Although 
the  distance  through  which  a  building  is  moved  may  not  exceed 
a  small  fraction  of  an  inch,  great  speed  is  attained  so  rapidly 
that  hardly  any  structure  can  withstand  it.  It  is  as  if  a  railroad 
train  should  start  from  a  state  of  rest  and  acquire  a  speed  of 
sixty  miles  an  hour  in  one  second.  When  an  earthquake  occurs 
in  the  sea  bottom  or  near  shore,  it  produces  enormous  waves 
which  may  be  as  destructive  as  the  quake  itself. 

In  Japan,  where  the  ground  seems  to  be  never  completely  still,  houses  are 
built  of  very  light  materials.  Structures  of  steel  and  concrete  upon  a  solid 
rock  foundation  are  least  liable  to  injury.  Buildings  of  brick  and  wood 
standing  upon  alluvial  or  newly  made  ground  are  most  dangerous.  Hun- 
dreds of  earthquakes  occur  every  year,  but  most  of  them  are  too  feeble  or 
too  remote  from  centers  of  population  to  do  serious  damage.  The  princi- 
pal areas  subject  to  destructive  earthquakes  are  shown  on  the  map,  Fig.  56. 

Physiographic  Provinces.  —  Fig.  57  shows  the  division  of  the 
land  according  to  structure,  and  indicates  broadly  the  causes  and 
character  of  rehef.  These  divisions  constitute  the  great  physio- 
graphic provinces  of  the  land.  This  map  should  be  compared 
with  the  relief  map.  Fig.  16. 


Old  Worn -down  Plains. 

Broken  Block  and  Old  Folded  Lands. 

Young  Folded  Mountains. 

Old  Unfolded  Table-lands. 

Old  Unfolded  Plains. 

Young  Plains  (largely  alluvial ). 


PHYSIOGRA 

After  HcrU 


AMERICA 


1.  Laurentian  Peneplain 
\  2.  Appalachian  Highland 

3.  Interior  Plain 

4.  Rocky  Mountains 

5.  Intermont  Plateaus 

6.  Pacific  Ranges 

7.  Coastal  Plain 


Caribbean  Ranges 
9,  Greenland  Plateau 

10.  Arctic  Archipelago 

11.  Andes  Mountains 

12.  Brazilian  Plateau 

13.  Guiana  Plateau 

14.  Interior  Plain 


PROVINCES 


EURASIA 

1.  Baltic  Peneplain  8.  Iranian  Plateaus 

2.  Scandinavian  Highland  9.  Mongol-Tibetan  Plateaus 

3.  Mediterranean  Highlands  10.  Indo-Chinese  Ranges 

4.  Western  Basins  and  Table-lands  11,  Chinese  Plateau 

5.  Baltic-Black  Plain  12.  Manchurian  Plateau 

6.  Interior  Plain  13.  Arabian  Plateau 

7.  Ural  Mountains  "  14.  Dekkan  Plateau 

15.  Caspian-Ob  Plains 

16.  East  Siberian  Plain 

17.  Chinese  Plain 

18.  Indus-Ganges  Plain 

19.  Mesopotamian  Plain 

20.  Malay  Archipelago 


AFRICA  AND  AUSTRALIA 

1.  Atlas  Mountains  6.  Rift  Valley 

2.  Central  African  Plateau    7.  Niger-Libyan  Plain 

3.  Saharan  Plateau  8.  Australian  Plateau 

4.  Kong  Plateau  9.  Australian  Mountains 

5.  Cape  Plateau  10.  Australian  Plain 


71 


CHAPTER  V 
GRADATION   BY  RUNNING   WATER 

Gradation.  —  If  a  building  lot  or  the  site  of  a  town  is  rough, 
it  is  generally  graded  by  cutting  down  the  hills  and  filling  up 
the  hollows.  The  same  process  of  grading  is  continually  going 
on  all  over  the  surface  of  the  land.  The  mountains  and  plateaus 
are  being  worn  down  and  the  material  is  carried  away  to  lower 
levels.  Valleys  and  basins  are  filled  and  plains  are  overspread 
with  the  waste  of  the  highlands.  The  lowest  and  largest  de- 
pressions of  the  earth  crust  are  occupied  by  the  oceans,  therefore 
the  process  of  gradation  will  not  stop  until  all  the  land  above 
sea  level  is  carried  away  and  deposited  on  the  sea  floor.  Thus 
it  happens  that  even  lowlands  are  being  eroded,  although  more 
slowly  than  highlands.  Lowering  the  level  of  the  earth  crust 
by  erosion  is  called  degradation;  raising  its  level  by  deposition 
is  called  aggradation;  and  the  result  of  the  two  processes  is 
gradation.  Gradation  is  a  very  complex  process  carried  on  by 
many  different  agents,  the  work  of  each  one  of  which  must  be 
studied  separately. 

Weathering  or  the  Disintegration  of  Rocks.  —  Wherever  bed 
rock  is  exposed  to  the  action  of  air,  water,  and  sun,  it  is  broken 
up  and  decomposed  into  loose  mantle  rock^  or  rock  waste.  The 
oxygen  of  the  air  attacks  some  rock  minerals,  especially  iron, 
which  rusts  and  crumbles  into  powder.  The  carbon  dioxide  of 
the  air  combines  with  lime  in  the  rocks  to  form  limestone,  which 
is  dissolved  away  by  water.  In  the  daytime  bare  rocks  become 
heated  by  the  sun  and  expand;  at  night  they  cool  rapidly  and 
contract.  This  change  of  volume  repeated  many  times  causes 
the  rocks  to  break  up  and  scale  off.  Water  frozen  in  pores  and 
cracks  breaks  rock,  as  it  breaks  pitchers  and  pipes  in  the  house. 

72 


GRADATION  BY   RUNNING  WATER 


73 


Fig.  58.  —  Frost  work,  Pikes  Peak,  Colorado. 

Mountain  peaks,  where  freezing  and  thawing  take  place  almost 
every  day,  are  shivered  to  pieces  and  crumble  into  a  heap  of 
ruins.  In  arid  regions  sand 
blown  by  the  wind  rapidly 
wears  away  the  hardest  rocks. 
Unprotected  telegraph  poles 
are  soon  cut  down  by  the 
sand  blast.  Unsupported  rock 
masses  are  broken  off  and 
pulled  down  by  gravity,  and 
are  reduced  to  smaller  frag- 
ments by  the  fall.  The  growth 
of  tree  roots  in  cracks  and 
the  acids  formed  by  decaying 
vegetation  help  on  the  process 
of  rock  destruction,  while  even 
burrowing  animals  contribute 
something  to  the  result.  The 
whole  combination  of  proc- 
esses by  which  massive  bed 
rocks  are  converted  into  man- 
tle rock  is  called  weathering,  and  its  products  are  clay,  sand, 
gravel,  pebbles,  and  boulders. 


Fig-  59-  —  Erosion  by  wind  and  sand. 

(The  Sphinx,  Egypt.) 


74 


PHYSICAL   GEOGRAPHY 


It  is  difficult  to  find  an  exposed  surface  of  rock  anywhere  which  has  not 
been  changed  by  the  weather  until  it  looks  quite  different  from  a  freshly 
broken  surface.  Old  monuments  in  cemeteries  show  the  effects  of  exposure 
to  air  and  rain.  Buildings  built  at  different  times  of  the  same  kind  of  stone 
often  reveal  their  relative  ages  by  changes  in  color  or  surface,  and  in  the 
course  of  centuries  stone  buildings  may  be  badly  damaged  by  the  weather. 

Movement  of  Mantle  Rock.  —  Mantle  rock  sometimes  re- 
mains in  the  place  where  it  is  formed,  and  may  accumulate  to 


Fig.  60.  —  Canon  and  talus  slopes,  Tongue  River,  Wyoming.     (Note  irrigation  conduit.) 

the  depth  of  many  feet.     Air  and  vegetable  acids,  carried  down 
into  the  cracks  and  crevices  of  bed  rock  by  ground  water,  extend 


GRADATION   BY  RUNNING  WATER 


75 


the  weathering  process  in  some  cases  hundreds  of  feet  below 
the  surface.  But  mantle  rock  is  always  in  a  condition  to  be 
moved  by  gravity,  wind,  or  water.  At  the  bottom  of  a  steep 
cliff  there  is  usually  a  talus,  or  heap  of  rock  fragments  fallen  from 
above.  On  mountain  sides  enormous  masses  of  rock  sometimes 
slide  down  at  once  and  bury  forests  and  houses  in  the  valley. 
Such  an  event  is  called  a  landslide.  Streams  of  stones  moving 
slowly  but  continuously  down  a  steep  slope  are  called  screes. 
Even  on  moderate  slopes  there  is  a  slow  creep  of  the  mantle  rock 


Fig.  6i.  —  Landslide,  Switzerland. 

downward.  Wherever  mantle  rock  is  fine  and  dry  the  wind 
blows  it  away,  drifting  sand  and  dust  into  dunes  and  ridges, 
spreading  them  over  the  neighboring  country  or  carrying  them 
out  to  sea.  Glaciers  transport  rock  fragments  of  all  sizes,  some 
as  large  as  a  house  and  some  as  fine  as  flour,  which  are  left  in  a 
heap  when  the  ice  melts. 
The  most  efficient  agent  in  transporting  mantle  rock  is  run- 


76  PHYSICAL   GEOGRAPHY 

ning  water.  The  rain  washes  dirt  into  the  streams,  which  buoy 
up  and  carry  away  great  quantities  of  clay,  sand,  and  gravel. 
The  swifter  the  stream,  the  coarser  the  material  it  can  carry. 
Even  large  boulders  are  rolled  over  one  another  and  along  the 
stream  bottom  (Fig.  65) .  Their  edges  and  corners  are  rounded  off 
and  the  whole  grist  is  rapidly  ground  finer.  Where  the  speed  of 
the  current  is  checked  a  part  of  the  load  is  dropped,  the  coarsest 
first;  and  gravel  or  sand  bars  and  mud  banks  are  built  up  along 
the  stream.  If  the  stream  flows  into  a  lake  or  the  sea,  its  current 
is  stopped  completely  and  all  its  load  of  sediment  settles  to  the 
bottom. 

Summary.  —  Thus,  by  the  various  processes  of  weathering  and 
erosion,  important  results  are  accomplished:  (i)  Soils,  com- 
posed of  various  mixtures  of  clay,  sand,  gravel,  and  humus,  are 
provided  for  the  growth  of  vegetation;  (2)  the  higher  places  of 
the  earth  crust  are  worn  down  or  degraded,  and  the  lower  places 
are  filled  up  or  aggraded;  (3)  during  this  process  of  gradation  the 
great  land  features  are  carved  and  molded  into  ever-changing 
patterns  of  relief. 

Valleys  and  Streams.  —  If  the  course  of  a  stream  is  followed 
up,  it  will  be  found  to  be  joined  at  intervals  on  either  side  by 
tributaries,  each  of  which  flows  in  a  valley  usually  proportioned 
to  the  size  of  the  stream.  The  main  stream  and  its  valley  grow 
smaller  above  the  mouth  of  each  tributary  until  they  are  reduced 
to  a  tiny  rivulet  flowing  in  a  furrow,  and  finally  come  to  an  end 
at  a  spring,  pond,  or  swamp,  or  upon  the  smooth  slope  of  a  hill- 
side. If  any  tributary  is  followed  up,  it  also  is  found  to  divide 
like  the  trunk  of  a  tree  into  smaller  branches  and  rivulets.  The 
surface  of  the  land  on  either  side  slopes  toward  the  stream  or 
one  of  its  tributaries,  and  at  the  same  time  there  is  a  continuous 
slope  downstream  from  the  head  or  tip  of  every  branch. 

If  the  slope  is  ascended  from  the  stream,  at  a  greater  or  less 
distance  a  point  is  reached  where  the  surface  begins  to  slope  away 
from  that  stream  toward  some  other  stream.  A  more  or  less 
definite  line  may  be  found  which  marks  the  junction  of  the  two 


GRADATION   BY   RUNNING   WATER 


77 


slopes  and  separates  the  water  flowing  into  one  stream  from  that 

flowing  into  the  other.     If  this  divide  or  water-parting  is  followed, 

it  is  found  to  pass  around  the  heads  of  all  the  tributaries  and 

to  inclose  the  hasin  or 

area  from  which  water 

drains  into  the  stream 

system. 

Run-off.  —  Some 
part  of  the  rain  fall- 
ing upon  any  basin 
evaporates,  a  part 
sinks  into  the  ground, 
and    the    remainder,  Fig.62.— Divide,  vigo  County,  ind. 

called  the  run-off,  flows  away  on  the  surface.  Some  of  the 
water  which  sinks  into  the  ground  comes  again  to  the  surface 
and  joins  the  run-off.  The  ratio  of  the  run-off  to  the  rainfall 
varies  with  the  slope,  structure,  climate,  and  vegetation  of  the 
basin. 

At  first  the  run-off  forms  a  thin  and  scarcely  perceptible  sheet ; 
but  it  soon  gathers  into  little  rills  which  join  one  another  and 
grow  larger  until  they  flow  into  one  of  the  permanent  branches 
of  the  stream  system.  The  smallest  branches  flow  only  while  it 
rains,  and  their  grooves  or  gullies  are  dry  most  of  the  time.  The 
permanent  branches  are  supplied  from  ponds,  swamps,  glaciers, 
or  springs. 

Near  the  sources  of  the  stream  the  slopes  are  apt  to  be  steep,  the  current 
swift,  the  channel  narrow  and  deep  and  perhaps  interrupted  by  rapids  and 
falls.  The  bed  is  strewn  with  boulders,  pebbles,  or  coarse  gravel  (Figs.  60, 
71,  73,  74,  77).  Farther  down,  as  the  slope  becomes  more  gentle,  the  bed  is 
smoother,  rapids  are  less  frequent  and  are  separated  by  long  reaches  of  quiet 
water,  and  the  channel  becomes  wider,  shallower,  and  more  crooked.  The 
loose  material  is  less  coarse  and  consists  chiefly  of  fine  gravel  and  sand.  Here 
the  watercourse  is  likely  to  become  double  and  to  consist  of  a  wide  outer 
valley  which  the  stream  covers  only  at  high  water,  and  through  which  the 
narrower  channel  winds  irregularly  from  side  to  side.  Still  farther  down, 
the  valley  may  become  very  much  wider  and  consist  of  an  extensive  flood 


78 


PHYSICAL    GEOGRAPHY 


Fig.  63.  —  Valley  with  bluffs,  New  York. 


plain  bounded  by  hlufs.  Here  the  ordinary  channel  follows  a  meandering 
course,  full  of  zigzag  bends  and  horseshoe  curves.  The  slope  is  gentle,  the 
current  sluggish,  and  the  bed  obstructed  by  sand  bars  and  mud  banks 
(Figs.  31,  32,  63,  70,  72,  75,  76).  The  stream  finally  flows  into  a  larger 
stream,  or  into  a  lake  or  the  sea. 

Transportation  of  Sediment.  —  A  stream  of  water  is  also  a 
stream  of  mantle  rock,  by  which  the  waste  of  the  land  is  running 
away  toward  the  sea.  Some  streams  are  clear,  but  they  always 
contain  a  small  quantity  of  invisible  mineral  matter  dissolved 
out  of  the  ground.  A  turbid  or  muddy  stream  is  carrying 
mantle  rock  in  suspension,  which  is  kept  from  sinking  by  ripples, 
eddies,  and  cross  currents  due  to  irregularities  in  the  bed.  Most 
rock  fragments  when  immersed  in  water  are  buoyed  up  to  the 
extent  of  about  one  third  of  their  weight,  and  are  therefore 
more  easily  moved  than  when  out  of  water.  (Lift  a  stone  out 
of  water  into  the  air.)  In  still  water  the  finer  particles  of  rock 
settle  more  slowly  than  the  coarser,  and  in  a  current  they  are 
carried  along  more  easily.  (Shake  up  clay,  sand,  and  gravel  in 
a  bottle  of  water  and  let  them  settle.)  The  size  of  the  particles 
of  rock  which  a  stream  can  carry  in  suspension  increases  rapidly 
as  the  speed  of  the  current  increases.  A  current  running  one  third 
of  a  mile  an  hour  can  carry  clay;  two  thirds  of  a  mile,  fine  sand; 
two  miles,  pebbles  as  large  as  cherries;  four  miles,  stones  as  large 
as  an  egg. 

A  swift  stream  can  carry  more  sediment  of  any  kind  in  suspension  than 
a  slow  one,  and  a  stream  of  any  speed  can  carry  a  larger  quantity  of  fine 


GRADATION  BY  RUNNING  WATER 


79 


sediment  than  of  coarse;  but  the  quantity  of  sediment  which  any  stream 
can  carry  is  limited.  A  stream  which  is  carrying  all  the  sediment  it  can  is 
said  to  be  loaded,  or,  less  appropriately,  overloaded.  If  the  speed  of  a 
stream  carrying  a  full  load  is  slackened,  its  carrying  capacity  diminishes 
rapidly,  and  it  immediately  drops  a  part  of  its  load,  arid  always  the  coarsest 
first.  If  a  current  carrying  a  mixed  load  of  clay,  sand,  and  gravel  is  grad- 
ually brought  to  a  standstill,  it  drops  the  coarse  gravel  first,  then  fine 
gravel,  then  coarse  sand,  then  fine  sand,  and  the  clay  last  of  all.  Thus 
running  water  is  the  most  efiicient  assorting  agent  known,  and  is  often 


Fig.  64.  —  stream  bed  with  banks  of  gravel  dropped  by  the  stream,  Parke  County,  Ind. 


used  for  that  purpose.  (Put  clay,  sand,  and  gravel  in  a  pan  of  water,  and 
by  stirring,  rinsing,  and  pouring  wash  out  the  clay  first  and  then  the  sand.) 
If  some  of  the  sediment  is  much  heavier  than  the  rest,  the  heavier  par- 
ticles are  left  behind,  while  larger  and  lighter  particles  are  carried  away. 
(Put  fine  shot  and  gravel  in  a  pan  of  water  and  wash  out  the  gravel.)  This 
is  the  reason  why  a  miner  can  "  pan  out "  coarse  gravel  and  have  fine  gold 
dust  left  in  his  pan.  If  rock  fragments  are  too  large  for  a  stream  to"  buoy 
up  and  carry,  it  may  push  and  roll  them  along  the  bottom. 

The  Speed  of  Streams.  —  A  stream  is  swifter  on  a  steep  slope 
than  on  a  gentle  one.  It  is  also  swifter  in  the  narrow  parts  of 
its  channel  than  in  the  wide  parts,  because  the  same  quantity 
of  water  must  pass  through  both  in  the  same  time.  Therefore 
any  stream  is  swifter  and  more  powerful  at  high  water  than  at 


8o 


PHYSICAL  GEOGRAPHY 


Fig.  6s.  —  Stream  bed  with  boulders. 

low  water.  The  greater  the 
volume  and  speed  of  a  stream, 
the  greater  the  quantity  and 
the  coarser  the  quality  of  the 
sediment  it  can  carry. 

In  times  of  flood,  streams  bring 
down  great  quantities  of  coarse 
material  which  they  are  obliged  to 
drop  as  the  flood  subsides.  When 
a  stream  is  low  in  summer,  it  may 
not  seem  to  be  carrying  any  sedi- 
ment at  all,  but  its  channel  may 
be  strewn  with  heaps  of  large  stones 
which  it  brought  down  at  the  last 
spring  flood.  If  a  slow  stream  is 
loaded  with  fine  sediment,  any  ob- 
struction, as  a  boulder,  log,  fallen 
treetop,  or  even  a  small  stake,  may- 
check  the  current  sufficiently  to 
cause  a  mud  or  sand  bar  to  be  de- 
posited on  the  downstream  side. 

Deposition.  —  All  the  sediment  carried  by  a  stream  must, 
sooner  or  later,  be  deposited  at  lower  levels.     Wherever  the 


Fig.  66.  —  Alluvial  cone. 


I 


GRADATION   BY  RUNNING  WATER 


8i 


current  is  checked  deposition  is  apt  to  occur.  A  stream  flow- 
ing down  a  steep  bank  rapidly  erodes  a  gully  and  deposits  the 
material  at  the  bottom  of.  the  bank  in  a  conical  or  fan-shaped 


Fig.  67.  —  Alluvial  fan,  Switzerland . 


heap.  Along  the  foot  of  a  mountain  range  this  process  some- 
times occurs  on  a  large  scale,  each  mountain  stream  building  a 
steep  alluvial  cone,  or  a  flat /aw  which  may  spread  out  several  miles. 


Fig.  68.  —  Contour  map  of  alluvial  fan.     (U.S.G.S.) 

Along  the  foot  of  the  Wasatch  Mountains,  in  Utah,  and  of  the  Sierra 
Nevada,  in  California,  the  alluvial  fans  are  so  large  as  to  touch  one  another, 
forming  a  continuous  piedmont  alluvial  plain.  An  alluvial  fan  sometimes 
affords  extraordinary  facilities  for  agriculture  by  irrigation.  The  water 
naturally  spreads  over  the  fan  and  can  be  easily  guided  to  any  part  of  it. 


^2 


l>ttYSICAL  GEOGRAPHY 


Fig.  69.  —A  part  of  the  Mississippi  delta.     Numbers  show  depths  in  fathoms. 

Whenever  a  stream  overflows  its  banks  it  deposits  sediment 
on  the  flooded  ground  and  forms  an  alluvial  plain,  which  in  the 


GRADATION  BY  RUNNING  WATER 


83 


lower  course  of  a  large  river  may  become  many  miles  in  width. 
At  the  mouth  of  a  river  the  alluvial  plain  may  extend  into  a 
lake  or  the  sea  in  the  form  of  a  delta,  which  is  a  flat  alluvial  fan 
built  in  the  water.  At  the  head  of  the  delta  the  stream  divides 
into  distributaries  and  enters  the  sea  by  many  mouths.  The 
surface  of  a  delta  cannot  be  raised  far  above  sea  level,  and  is 
liable  to  be  flooded  by  the  river  and  by  tides.  The  soil  of  delta 
lands  is  so  fertile  that  it  is  often  profitable  to  protect  them  by 
dikes  or  embankments,  as  has  been  done  on  a  large  scale  at  the 
mouth  of  the  Rhine. 

Sediment  deposited  by  water  is  always  more  or  less  completely  assorted, 
the  finer  from  the  coarser,  and  deposited  in  nearly  horizontal  strata.  The 
stratified  rocks  which  form  a  large  part  of  the  earth  crust  are  nearly  all 
made  from  sediment  deposited  by  water. 


i^. 

.Xil 

1  ' 

^.^"V^-; 

MBj 

KrI 

-"^W 

H 

f 

%0%\\ 

m^ 

«.  /w/ .:' 

^m-_ 

^_. 

^ 

C 

■^ 

^    '     w 

m^u 

^         :4 

* 

"" 

'^ 

^ 

■% 

k.„ 

Hife~ 

^'m 

"    '■      /.. 

:^ 

.\ 

HK^^*;  '     '-Jij^ 

i 

^J 

Fig.  70.  —  Cut  banks  and  bars. 


The  Crookedness  of  Streams.  —  The  movement  of  water  in 
a  stream  is  retarded  by  friction  against  the  bottom  and  banks, 
and  against  the  air  on  the  upper  surface.     Therefore  the  water 


84 


PHYSICAL  GEOGRAPHY 


Fig.  71.  —  Gully  in  gravel. 


moves  fastest  a  little  below  the  surface  and  along  the  line  of  the 
deepest  channel.  A  flowing  stream  cannot  be  straight,  because 
there  is  sure  to  be  more  resistance  on  one  side  than  on  the  other, 
and  a  small  obstruction  is  sufficient  to  turn  the  current  toward 

the  opposite  bank.  A 
strong  stream  on  a  steep 
slope  is  not  easily  turned 
aside  and  is  compara- 
tively straight,  but  the 
same  stream  on  a  gentle 
slope  meanders  from  side 
to  side  and  becomes  very 
crooked.  In  a  winding 
stream  the  current  is 
swifter  on  the  outside  of 
the  bend,  and  there  it 
cuts  away  the  bank  and 
deepens  its  channel.  On  the  inside  of  the  bend  the  slower 
current  is  unable  to  carry  its  load  and  builds  up  a  sloping  bar 
of  mud  or  sand.  In  this  way  the  stream  is  constantly  shifting 
its  channel  sidewise  and  widen- 
ing its  valley. 

Valley  Forms.  —  A  clear 
stream  running  over  bed  rock 
may  dissolve  it  slowly,  but  a 
stream  carrying  a  moderate 
load  of  sand  and  gravel  uses 
them  as  tools  with  which  it 
saws  or  files  its  way  down 
through  the  hardest  rocks.  A 
swift  stream  erodes  faster  at 
the  bottom  than  at  the  sides,  and  cuts  a  deep,  narrow  valley. 
A  slow  stream  is  usually  unable  to  sweep  its  bed  clear  of  sedi- 
ment and  therefore  cannot  cut  it  deeper.  Its  energy  is  expended 
in  wearing  away  its  banks,  and  in  this  way  a  small  stream  may 


Fig.  72.  —  Meandering  stream. 


Fig-  73-  —  Portion  of  the  Grand  Canon  of  the  Colorado,  and  the  mouth  of  the  canon  of 

the  Little  Colorado  River.     Scale  about  i  mile  per  inch.     Contour  interval  50  feet. 

(Vishnu,  Arizona,  Sheet,  U.S.G.S.) 

85 


&6 


PHYSICAL   GEOGRAPHY 


in  the  course  of  time  make  a  wide  valley.  Its  work  may  be 
done  so  slowly  that  scarcely  any  change  is  noticeable  in  a  life- 
time, but  if  it  carries  away  only  ten  wagon  loads  of  dirt  from 

each  mile  of  its  course  in  a 
year,  it  can,  in  50,000  years, 
make  a  valley  100  feet  wide 
and  25  feet  deep. 

A  small  but  deep  and  narrow 
valley  is  called  a  ravine  or  gorge. 
In  plateaus  and  mountains  rivers 
are  able  to  cut  cafions  of  enormous 
dimensions.  The  Colorado  River 
flows  for  about  1000  miles  through 
a  series  of  canons,  of  which  the 
Grand  Caiion  in  Arizona  is  prob- 
ably the  most  extensive  cut  any- 
where in  the  face  of  the  earth.  It 
is  217  miles  long,  eight  to  fifteen 
miles  wide,  and  about  one  mile 
deep.  The  river  is  not  utilizable 
for  navigation  or  irrigation,  but 
the  scenery  of  the  canon  is  unsur- 
passed for  grandeur  and  beauty. 
The  depth  of  the  cut  and  the 
length  of  the  main  canon  and  its 
tributaries  present  an  exposure  of 
rock  strata  so  clear  and  extensive 
that  geographers  and  geologists  have  probably  learned  more  about  the 
structure  of  the  earth  crust  and  the  process  of  erosion  from  the  Colorado 
caiions  than  from  any  other  region  in  the  world. 

Upper,  Middle,  and  Lower  Parts  of  a  Valley.  —  The  head- 
waters of  a  large  river  are  generally  in  highlands  where  the 
slopes  are  steep.  The  tributaries  have  a  rapid  fall  and  are  often 
rushing  torrents.  Their  erosive  power  is  very  great,  but  their 
volume  is  small.  The  valleys  they  cut  are  deep,  narrow,  strewn 
with  large  boulders,  and  interrupted  by  falls.  In  the  middle 
part  of  its  course  the  slope  is  more  gentle,  but  the  volume 
of  water  is  larger,  and  it  is  here  that  the  greatest  amount  of 


Fig.  74. 


-  Royal  Gorge,  Colorado. 

3000  feet  deep. 


GRADATION  BY  RUNNING  WATER 


87 


erosion  takes  place.  The  river  carries  away  such  quantities  of 
sediment  that  its  valley  becomes  both  deep  and  wide.  In  the 
lower  course  the  slope  is  very  gentle,  the  current  is  feeble,  and 


Fig.  75-  —  Low  water,  Wabash  River,  Terre  Haute,  Ind. 

the  load  too  great  to  be  carried.  The  land  surface  is  not  far 
above  sea  level,  below  which  the  river  cannot  deepen  its  valley. 
The  current  is  continually  obstructing  itself  by  its  deposits  of 


Fig.  76.  —  High  water,  Wabash  River,  Terre  Haute,  Ind. 

sediment,  which  compel  it  to  shift  its  channel.  It  cuts  away 
its  bank  in  one  place  and  builds  it  up  in  another,  developing  a 
wide  flood  plain  bounded  by  bluffs. 

A  stream  which  is  actively  deepening  its  valley  is  young  (Figs. 


88 


PHYSICAL  GEOGRAPHY 


Fig.  77.  —  Young  valley.     (Forty  Mile  Creek,  Alaska.) 


60,73,74,77,79,83). 

A  stream  which  has 
deepened  its  valley  as 
far  as  possible,  and 
has  smoothed  out 
rapids  and  falls,  has 
reached  base  level  and 
is  mature  (Figs.  63, 
78,79,95).  A  stream 
which  is  widening  its 
valley  and  aggrading 
its    flood    plain    has 

reached  a  condition  of  old  age  (Figs.  31, 32,  64,  72,  79,  94,  97,  98). 
Playfair^s  Law.  —  The  relation  of  valleys  and  streams  was 

stated  by  John  Playfair  in  1802: 

"  Every  river  appears  to  consist  of  a  main  trunk  fed  from  a  variety  of 
branches,  each  running  in  a  valley  proportioned  to  its  size,  and  all  of  them 
together  forming  a  system  of  valleys,  communicating  with  one  another,  and 
having  such  a  nice  adjustment  of  their  slopes  that  none  of  them  join  the 
principal  valley  either  on  too  high  or  too  low  a  level:  a  circumstance  which 
would  be  infinitely  improbable  if  each  of  these  valleys  were  not  the  work  of 
the  stream  which  flows  through  it." 

Streams  and  Relief.  —  The  first  effect  of  stream  erosion  upon 
the  land  surface  is  to  cut  it  up  into  a  system  of  valleys  with 
broad  ridges  or  divides  between.  As  the  valleys  grow  deeper 
and  wider,  the  divides  grow  narrower  and  are  gradually  eaten 
away  until  their  crests  are  sharp;  the  whole  surface  consists  of 
slopes,  and  traveHng  across  it  is  "  all  uphill  and  down."  When 
the  surface  has  been  made  as  rough  as  possible  and  there  is 
little  or  no  level  land  left,  it  is  said  to  be  maturely  dissected,  or 
simply  mature  (Fig.  78)*  After  the  stage  of  maturity,  continued 
stream  work  makes  the  divides  lower  and  the  valley  bottoms 
wider.  The  country  begins  to  grow  smoother,  and  in  the  course 
of  time  is  reduced  to  a  plain  of  low  relief,  not  far  above  sea 
level  (Figs.  29,  30,  79,  in),  called  a  peneplain  (almost  a  plain). 


Fig.  78.  —  Maturely  dissected  plateau,  and  graded  valley,  Ohio  and  West  Virginia. 

Scale  about  i  mile  per  inch.     Contour  interval  20  feet.     (Athalia  Sheet,  U.S.G.S.) 

89 


90  PHYSICAL  GEOGRAPHY 

During  the  earlier  stages  of  stream  erosion  the  land  surface  is 
made  rougher,  during  the  later  stages  it  is  made  smoother,  and 
the  final  result  is  to  degrade  the  land  and  aggrade  the  sea 
bottom,  until  they  are  both  graded  nearly  to  sea  level. 

Upon  a  completely  graded  peneplain  the  processes  of  stream  erosion 
cease,  because  the  streams  have  no  longer  a  slope  sufficient  to  enable  them 
to  carry  sediment.  But  if  a  peneplain  is  uplifted  by  internal  forces  the 
revived  streams  will  begin  the  process  of  gradation  all  over  again.  Gra- 
dation goes  on  most  rapidly  on  mountains  because  weathering  is  more 
active  there,  and  the  slopes  are  so  steep  that  gravity  and  running  water 
can  pull  down  and  carry  away  great  quantities  of  mantle  rock.  Conse- 
quently mountains  do  not  last  long,  and  all  high  mountains  are  compara- 
tively young.  For  the  same  reasons,  plateaus  are  degraded  more  rapidly 
than  plains.  Heavy  rainfall  favors  rapid  degradation  because  water  helps 
to  decompose  and  wash  away  rocks,  and  streams  are  larger  and  more 
numerous  in  wet  regions.  Some  kinds  of  rocks  are  more  resistant  to  weath- 
ering and  erosion  than  others,  and  are  left  projecting  as  the  general  surface 
is  lowered.  A  covering  of  forest  or  other  vegetation  generally  retards 
erosion. 

Economic  Relations.  —  The  value  of  a  region  for  human  occu- 
pation depends  largely  upon  the  stage  of  gradation  it  has  reached. 
Young,  low  plains  are  smooth,  gently  sloping,  easily  accessible, 
and  generally  productive.  The  work  of  gradation  progresses 
slowly  and  can  never  produce  a  surface  of  strong  relief.  All 
human  occupations  may  be  carried  on  with  ease,  and  in  all  stages 
plains  are  fitted  to  support  a  large  population  with  a  minimum 
expenditure  of  energy. 

Young  plateaus  of  moderate  height  are  second  in  value  only 
to  plains.  Gradation  begins  as  soon  as  the  surface  is  exposed 
above  the  sea,  goes  on  during  the  long,  slow  process  of  upheaval, 
and  usually  before  any  great  height  is  reached  has  progressed 
so  far  as  seriously  to  roughen  the  surface.  As  dissection  of  the 
plateau  approaches  maturity,  it  is  cut  up  into  an  intricate  system 
of  deep  valleys  and  narrow  ridges,  which  is  as  inconvenient  as 
possible  for  carrying  on  any  kind  of  human  business  (Figs.  43, 
78,  79).  In  the  stages  beyond  maturity,  as  old  age  approaches, 
the  relief  of  a  plateau  becomes  smoother,  and  as  a  peneplain  it 


GRADATION  BY  RUNNING  WATER  .9I 

finally  reaches  a  condition  not  essentially  different  from  that  of 
a  region  originally  a  low  plain. 

Most  young  mountains  are  high  and  extremely  rugged,  like 
the  Alps,  and  are  of  all  regions  the  most  difhcult  of  utilization 
by  man.     In  some  young  mountains,  like  the  Jura  (Fig.  39), 


Fig.  79.  —  Youth,  maturity,  and  old  age. 

the  earth  crust  has  been  less  violently  disturbed,  folded,  and 
broken,  and  the  region  is  correspondingly  less  forbidding.  Such 
regions  pass  through  changes  somewhat  like  those  of  a  plateau. 
As  a  rule,  it  is  only  in  old  age  that  mountain  regions  become  so 
far  worn  down  and  smoothed  off  as  to  be  fitted  for  occupation 
by  any  large  number  of  people.  The  Appalachians  furnish  a 
notable  example  of  an  old  mountain  region.  The  general  law  is 
obvious  that  lowlands  are  the  homes  of  the  most  highly  civilized 
peoples. 


Fig.  80.  —  Niagara  Falls  and  Gorge.     Scale  about  1.25  miles  per  inch. 

Contour  interval  20  feet.     (Niagara  Falls  Sheet,  U.S.G.S) 

92 


GRADATION  BY  RUNNING  WATER 


93 


Waterfalls.  —  Wherever  the  slope  of  a  stream  bed  is  abrupt 
or  steep,  falls  and  rapids  occur.  They  are  usually  due  to  an 
outcrop  of  resistant  rock  which  the  stream  cannot  wear  down 
as  rapidly  as  the  softer  material  in  other  parts  of  its  course. 
In  a  brook  a  tree  root  or  a  bed  of  clay  on  top  of  sand  will  make 
a  fall.  Glaciated  valleys  are  often  bordered  by  chffs  over  which 
streams  cascade.  Such  falls  are  sometimes  of  great  height,  like 
those  of  the  Yosemite  Valley  in  California  (Figs.  84,  105),  and 
many  in  Norway.  Falls  and  rapids  in  large  rivers  generally 
occur  where  the  stream  crosses  a  bed  of  limestone,  granite,  or 
lava.  The  force  of  the  falling  water  deepens  the  channel  below 
the  falls  and  undermines  the  cliff  behind  them,  so  that  the  falls 
retreat  upstream,  leaving  a  gorge  below  (Figs.  80,  81,  82,  86). 


Fig.  8i.  —  Gorge  of  Niagara  River,  made  by  retreat  of  the  Falls. 

The  Niagara  River  falls  over  a  limestone  ledge  into  a  gorge  400  feet  deep 
and  seven  miles  long,  which  the  river  has  cut  by  the  migration  of  the  falls  up- 
stream. The  gorge  below  the  Victoria  Falls  on  the  Zambezi  River  in  Africa, 
500  feet  deep  and  40  miles  long,  has  a  peculiar  zigzag  course  on  account  of 
cracks  in  the  bed  of  lava.  Rapids  and  falls  are  most  numerous  in  moun- 
tains and  plateaus,  and  in  young  streams  everywhere.  An  old  stream  has 
had  time  enough  to  wear  down  and  smooth  out  the  irregularities  of  its  bed. 


94 


PHYSICAL  GEOGRAPHY 


Economic  Relations.  —  Waterfalls  are  becoming  more  and 
more  valuable  as  sources  of  power  for  running  machinery.     Most 

of  them  are  not  easily 
available  because 
they  occur  in  remote 
and  inaccessible  re- 
gions, but  if  the  power 
cannot  be  brought  to 
the  present  site  of  an 
industry,  the  industry 
may  be  moved  to 
the  place  where  the 
power  is. 

Of  all  the  water  powers 
in  the  world  that  of  Niag- 
ara Falls  is  the  most  val- 
uable, because  of  the  large 
and  constant  volume  of 
water,  and  still  more  be- 
cause it  is  situated  in  the 
midst  of  a  densely  popu- 
lated district.  A  part  of  their  power  is  now  used  to  generate  electricity 
which  is  transmitted  over  wires  to  run  railroads  and  factories,  and  to  fur- 
nish light  to  cities  within  150  miles.  There  is  power  enough  at  Niagara  to 
supply  four  or  five  of  the  largest  cities  in  America. 

Waterfalls  are  among  the  most  attractive  scenic  features  of 
the  world  and  have  a  high  value  apart  from  any  use  that  can  be 
made  of  their  power.  On  account  of  their  beauty  and  grandeur 
and  because  they  are  so  easily  accessible,  Niagara  Falls  are  visited 
by  about  600,000  people  every  year.  The  use  of  the  water  for 
power  seriously  impairs  their  beauty  and  might  entirely  destroy 
it.  Whether  it  would  be  better  for  the  human  race  to  keep  the 
falls  in  their  natural  state  to  give  pleasure  to  future  millions,  or 
to  destroy  them  by  diverting  the  water  for  power  purposes,  is 
an  important  practical  question  which  the  present  generation 
is  called  upon  to  decide. 


Copyright  by  Duubleday,  Page  &  Co. 

Fig.  82.  —  Gorge  of  the  Zambezi. 


CHAPTER  VI 
THE  ECONOMIC  RELATIONS  OF  STREAMS 

Drainage.  —  The  first  important  function  of  streams  is  to 
drain  the  land  by  carrying  surplus  rain  water  to  the  sea.  When 
a  land  surface  is  first  exposed  to  stream  action  by  elevation  above 
the  sea,  or  by  the  melting  of  an  ice  cap,  the  drainage  is  imperfect. 
Depressions  are  occupied  by  lakes,  ponds,  and  marshes,  which, 
if  numerous,  are  sure  indications  of  youthful  drainage. 

The  glaciated  regions  of  northern  North  America  and  Europe  and  the 
recently  elevated  land  of  Florida  are  conspicuous  examples.  On  low  plains 
and  gentle  slopes  drainage  develops  slowly  and  remains  imperfect  for  a 
long  time.  The  shallow  lakes  of  the  glacial  drift  are  being  filled  with  accu- 
mulations of  mud  and  peat  which  promise  to  be  of  value  in  the  future 
for  cement  and  fuel.  Wet,  undrained  land  is  comparatively  worthless  for 
human  occupation.  It  produces  at  best  only  inferior  timber  or  coarse 
herbage.  Artificial  drainage  by  open  ditches  and  tile  drains  may  convert 
such  land  into  excellent  farms  and  gardens.  The  area  of  marsh  lands  in 
the  United  States  which  might  be  drained  is  larger  than  the  area  of  arid 
lands  that  can  be  irrigated. 

In  a  mature  drainage  system  every  part  of  the  land  is  drained, 
and  any  drop  of  rain  falling  upon  its  basin  may  find  its  way 
to  the  sea.  On  plateaus  and  in  mountainous  and  hilly  regions, 
slopes  are  steep  and  drainage  is  often  too  rapid.  The  soil  is 
washed  away,  the  surface  is  cut  up  by  gullies,  and  the  lowlands 
are  buried  in  sand  and  gravel.  In  the  old  countries  where  soil 
is  precious  this  waste  is  sometimes  checked  by  a  series  of  dams. 
Such  areas  ought  to  be  used  for  the  growth  of  forests,  which 
retard  the  run-off  and  prevent  waste  by  erosion. 

Erosion.  —  Streams  are  not  currents  of  running  water  only, 
but  also  of  running  rock.  Through  them  the  solid  land  is  drain- 
ing away*  to  the  sea.     Everywhere  except  in  desert  regions  the 

95 


96  PHYSICAL  GEOGRAPHY 

details  of  landscape  are  due  to  stream  or  glacial  action.  Valleys 
are  cut  in  the  earth  crust,  thus  making  its  materials  accessible, 
revealing  its  structure,  and  producing  a  great  variety  of  scenery. 
Rocks  and  minerals  originally  buried  far  below  the  surface  have 
been  uncovered  and  exposed.     There  would  be  no  coal  mines  in 


Fig.  83.  —  Watkins  Glen,  New  York:     A  very  young  gorge  in  shale  rock. 

Pennsylvania  if  streams  had  not  removed  from  the  surface  of 
that  region  beds  of  rock  several  miles  in  thickness.  The  cuts 
made  by  streams  into  the  earth  crust  are  invaluable  to  the 
geologist,  because  he  finds  there  exposed  all  kinds  of  rocks  and 
is  able  to  study  their  composition  and  arrangement,  to  deter 
mine  their  origin  and  history,  and  to  learn  how  the  earth  has 
been  made.  He  finds  in  the  rocks  the  fossil  remains  of  thou- 
sands of  plants  and  animals  which  no  human  being  'ever  saw 


97 


98 


PHYSICAL  GEOGRAPHY 


Fig.  85.  —  Red  Butte,  Nebraska.    (U.S.G.S.) 


alive,  and  is  able  to  read  the  history  of  life  on  the  earth  during 
past  millions  of  years. 

If  it  were  not  for  stream  erosion 
the  surface  of  the  land  would  be 
as  monotonous  and  uninteresting 
as  the  bottom  of  the  sea.  There 
would  be  no  ravines,  gorges,  caiions, 
cliffs,  buttes,  mesas,  spurs,  passes, 
or  peaks.  Even  mountain  ranges 
would  be  tame  and  unimpressive. 
The  most  famous  scenery  in  the 
world,  the  Grand  Canon,  the  Yo- 
semite  Valley,  the  Niagara  Falls 
and  Gorge,  the  valleys  of  the  Hudson  and  the  Rhine,  the  Scotch  Highlands, 
the  English  and  Italian  lakes,  the  fiords  of  Alaska  and  Norway,  would  not 
be  in  existence.  Few  things  in  nature 
are  more  attractive  to  men  than  run- 
ning water.  Without  it  the  world 
would  be  a  much  less  pleasant  place 
to  live  in. 

Water  Supply.  —  One  of  the 
prime  requisites  for  plant  or 
animal  life  is  an  adequate 
water  supply.  Many  species 
of  shellfish,  fish,  frogs,  insects, 
waterfowl,  and  higher  animals, 
from  the  muskrat  to  the  hip- 
popotamus, find  in  streams  a 
home  and  a  storehouse  of  food. 
All  the  higher  animals  visit 
them  frequently  to  drink.  The 
hunter  in  pursuit  of  game, 
whether  it  be  duck,  deer,  gi- 
raffe, lion,  or  elephant,  lies  in 
wait  by  the  water's  edge,  where 

he  knows  thirst  will  bring  his  victim  in  due  time.  A  man  con- 
sumes nearly  a  gallon  of  water  a  day,  and  if  it  happens  to  con- 
tain the  germs  of  disease  it  may  be  a  fatal  poison  as  well  as  a 


Fig.  86. 


Taghannock  Falls  and  Gorge, 
New  York. 


I 


THE   ECONOMIC   RELATIONS   OF   STREAMS 


99 


LONG  VALLEY       ^^ikt, 
RESERVOIR  <>X^" 


k 


"m 


food.  Travel  and  settlement  have  been  strongly  influenced  by 
water  supply.  Springs  have  determined  the  location  of  trails, 
camps,  homesteads,  and  villages. 

Scattered  and  rural  populations 
depend  generally  upon  ground  water 
obtained  from  wells,  but  in  cities, 
where  thousands  or  millions  of  people 
are  crowded  together  upon  a  few 
square  miles,  wells  are  inadequate 
and  dangerous.  Large  cities  must 
almost  always  depend  upon  streams 
for  water  supply.  A  lake  forms  a 
natural  reservoir  of  generally  clear, 
pure  water,  and  if  necessary  an  arti- 
ficial lake  can  be  made  by  means  of 
a  dam. 

Few  cities  are  so  fortunate  as  Chicago  in 
having  a  fresh-water  sea  at  its  doors.  Yet 
Chicago  has  had  to  reach  out  under  the  lake 
with  a  tunnel  six  miles  long  to  obtain  water 
free  from  pollution,  and  to  spend  thirty  mil- 
lion dollars  on  a  canal  to  carry  away  its 
drainage.  St.  Louis  and  New  Orleans  have 
the  mighty  flood  of  the  Mississippi  to  draw 
upon.  The  water  is  muddy,  but  the  mud  is 
harmless  and  can  be  filtered  out.  New  York 
has  taken  possession  of  the  Croton  River 
basin,  and  is  now  preparing  to  bring  a  larger 
supply  from  the  Catskills.  Glasgow  brings 
water  from  Loch  Katrine,  42  miles,  Man- 
chester from  Thirlmere,  96  miles,  and  Liver- 
pool from  artificial  Lake  Vyrnwy,  67  miles. 
Los  Angeles  is  constructing  an  aqueduct  250 
miles  long,  and  tunneUng  through  a  moun- 
tain range,  to  get  water  from  Owens  River. 
London  has  sanitary  control  of  the  whole  Thames  basin,  which  is  hardly 
adequate  to  supply  water  to  seven  millions  of  people.  No  city  can  afford 
to  spare  pains  or  expense  to  obtain  a  sufficient  and  safe  water  supply. 


; LOS  ANGELES 

=^fiSi^Sauta  Monica' 

Scale  of  Miles 


Fig.  87.  —  Los  Angeles  aqueduct. 


lOO  PHYSICAL   GEOGRAPHY 

Food  Supply.  —  Nearly  all  streams  contain  fish  of  some  kind, 
and  in  large  rivers  and  lakes,  such  as  the  St.  Lawrence  system, 
fisheries  form  an  important  source  of  food  supply.  The  rivers 
of  the  Pacific  coast  of  America,  from  the  Sacramento  northward, 
once  furnished  in  the  form  of  salmon  one  of  the  most  abundant 
food  supplies  in  the  world.  The  United  States  Fish  Commis- 
sion, and  similar  bureaus  in  other  countries,  have  been  organized 
to  preserve  and  increase  the  supply  of  fish  food  by  distributing 
eggs  and  fry  and  by  regulating  seasons  and  methods  of  fishing. 

Travel  and  Transportation.  —  Streams  furnish  easy  routes  of 
travel  and  transportation.  In  new  and  undeveloped  countries 
they  are  often  the  only  practicable  routes.  They  are  extensions 
of  sea  facilities  into  the  land,  and  of  lowlands  into  highlands. 
Explorers,  from  Hudson,  Champlain,  and  La  Salle  to  Livingstone 
and  Stanley,  have  penetrated  the  continents  by  way  of  great 
rivers.  After  a  country  has  been  long  occupied  by  civilized 
people,  rivers  still  remain  cheap  and  ready-made  freight  routes, 
without  expense  for  construction  and  maintenance. 

The  Amazon  admits  large  vessels  2,000  miles  into  the  interior  of  Brazil, 

and,  with  its  many  large  tributaries,  constitutes  the  only  means  of  travel 

through  an  area  nearly  as  large  as  the  United  States.     The  Belgian  Kongo 

is  being  opened  to  trade  and 

civilization  by  means   of  its 

rivers.     In  China  one  fourth 

of    the    human    race    depend 

upon   their   great   waterways 

for  circulation  of  people  and 

goods.     In  Europe  the  Seine, 

Rhine,    Elbe,    Danube,    and 
Fig.  88.-Railroad  following  grade  of  Allegheny         y^j^^  ^^^   ^^_^^y  ^^^^^  l^jgj^. 

ways  of  commerce.  North 
America  has  been  setded  largely  through  its  great  rivers,  and  while  water 
transportation  is  now  to  a  great  extent  superseded  by  railroads,  the  St. 
Lawrence  and  the  Great  Lakes  transport  as  many  tons  of  freight  as  the 
Mediterranean  Sea. 

Rivers  have  been  at  work  for  ages  grading  their  valleys,  and 
when  man  undertakes  artificial  highways  he  avails  himself  of 


THE   ECONOMIC  RELATIONS  OF  STREAM5>  ' 


lOi 


their  work.  Canals  and  railways  follow  stream  valleys  wher- 
ever possible.  Their  construction  would  be  everywhere  more 
costly,  and  in  rough  and  mountainous  countries  impossible,  if  the 
streams  had  not  first  cleared  the  way.  Nearly  every  important 
city  in  the  world  is  located  upon  a  river  and  stands  where  it  does 
because  of  the  river. 

Water  Power.  —  Wherever  water  runs  downhill,  the  force  of 
gravity  or  the  weight  of  the  water  can  be  used  to  drive  machinery. 


Fig.  89.  —  Water  power  on  Genesee  River,  Rochester,  N.  Y. 


The  most  valuable  water  powers  are  found  at  natural  cataracts 
or  rapids  where  the  fall,  usually  distributed  over  many  miles, 
is  concentrated  in  a  small  space.  In  the  absence  of  natural 
rapids  or  falls,  an  artificial  fall  must  be  made  by  means  of  a  dam. 
For  this  purpose  swift  streams  with  deep,  narrow  valleys,  like 
those  of  New  England,  are  most  advantageous.  Abundant 
water  power,  with  few  exceptions,  is  found  in  highlands  and 
along  the  upper  courses  of  streams.     For  this  reason  moun 


162  '         '     PHYSICAL  GEOGRAPHY 

tainous  countries  such  as  Switzerland,  Italy,  and  Norway  are 
becoming  important  manufacturing  centers. 

Irrigation.  —  To  have  water  to  use  whenever  needed  is  an 
ideal  condition  for  raising  any  crop,  and  is  far  better  than  de- 
pendence upon  irregular  and  uncertain  rainfall.     Irrigation  is  as 


Fig.  90.  —  Irrigating  ditches  in  orange  grove,  Arizona. 

old  as  civilization.  It  is  a  remarkable  fact  that  the  localities 
where  civilization  first  appeared  were  deserts  which,  in  their 
natural  state,  were  almost  uninhabitable. 

Six  or  seven  thousand  years  ago  men  learned  to  make  use  of  the  over- 
flow upon  flood  plains  and  to  improve  and  extend  the  natural  process 
by  means  of  reservoirs,  canals,  and  ditches.  In  the  valleys  of  the  Tigris, 
Euphrates,  and  Nile,  populous  and  powerful  communities  depended  for 
existence  upon  irrigation.  In  the  present  century  the  British  in  Egypt 
have  constructed  immense  dams  which  retain  enough  water  to  make  thou- 
sands of  acres  of  desert  productive.  The  Turkish  government  is  under- 
taking similar  works  to  restore  the  ancient  prosperity  of  Mesopotamia^. 
Irrigation  has  been  practiced  from  time  immemorial  in  Turkestan,  India, 
Spain,  Italy,  and  Mexico.  The  United  States  government  is  now  engaged 
in  the  construction  of  an  extensive  system  of  irrigation  works  which  will 
result  in  the  reclamation  of  millions  of  acres  of  arid  land.  Irrigation  on  a 
large  scale  is  possible  only  in  the  lower  courses  of  rivers  where  the  valley 
is  wide,  or  on  plains  and  plateaus  bordered  by  mountains  from  which  the 
water  may  be  distributed  over  the  land. 


THE   ECONOMIC  RELATIONS   OF  STREAM? 


103 


The  Utilization  of  Rivers.  —  A  river  is  most  usable  for  naviga- 
tion when  it  has  a  large  and  comparatively  constant  volume  of 
water,  a  small  or  moderate  load  of  sediment,  a  graded  slope,  a 
gentle  current,  and  a  wide,  shallow  valley.  Such  rivers  occur 
in  plains  and  low  plateaus  of  medium  or  heayy  rainfall.  A  lake 
in  the  course  of  a  river  adds  greatly  to  its  advantages.  The 
lake  is  wide,  its  water  is  deep  and  still,  and  its  surface  is  level. 
The  river  below  the 
lake  is  clear  and  not 
subject  to  floods  or 
low  stages  of  water. 
Drowning  of  the 
lower  part  of  a  river 
valley  produces  con- 
ditions similar  to 
those  of  a  lake. 

In  the  possession  of 
these  characteristics  the 
St.  Lawrence  is  preemi- 
nent among  the  rivers  of 
the  world.  Its  valley  is 
drowned  to  a  point  900 
miles  from  the  sea,  and 
the  five  Great  Lakes  have  an  aggregate  length  cf  nearly  1,500  miles,  leaving 
only  300  miles  of  the  system  with  any  perceptible  current.  In  sailing  from 
Buffalo  to  Chicago,  a  distance  of  800  miles,  a  vessel  ascends  only  eight  feet, 
or  to  Duluth,  a  still  greater  distance,  only  thirty  feet. 

In  most  streams  there  is  some  variation  of  volume  dependent 
upon  seasonal  rainfall,  snow  melting,  and  evaporation.  In  the 
middle  latitudes  of  Europe  and  eastern  North  America,  high 
water  is  due  to  winter  rains,  or  melting  snow  on  frozen  ground, 
and  occurs  in  the  late  winter  or  spring.  The  Ohio,  Seine,  Rhine, 
Elbe,  and  Danube  belong  to  this  group.  The  rivers  of  northern 
North  America  and  Eurasia  derive  their  main  water  supply 
from  melting  snow  and  have  high  water  in  the  spring.  The 
floods  are  made  much  more  extensive  and  prolonged  by  great 


Fig.  91.  —  Lake  steamer. 


164  PHYSICAL  GEOGRAPHY 

ice  dams  in  their  lower  courses,  which  persist  and  hold  the  water 
back  long  after  the  upper  courses  are  clear  of  ice.  On  account 
of  such  conditions  these  rivers  are  of  little  use.  They  include 
the  Yukon,  Mackenzie,  Saskatchewan-Nelson,  Dwina,  Petchora, 
Ob,  Yenisei,  and  Lena. 

In  the  tropical  regions  of  South  America  and  Africa  and  the 
monsoon  regions  of  Asia  high  water  occurs  with  the  heavy  rains 
of  summer.  The  rivers  of  this  class  include  the  Orinoco,  Amazon, 
Parana,  Kongo,  Zambezi,  Nile,  Ganges,  Brahmaputra,  Yangtse, 
Hoang,  and  Amur. 

Rivers  in  mountains  and  high  plateaus  are  utilizable  chiefly 
for  power  in  their  upper  courses  and  for  irrigation  in  their  lower. 
Their  main  water  supply  is  from  melting  snow,  and  they  are 
subject  to  great  changes  of  volume.  The  most  important  flow 
from  the  interior  highlands  of  North  America  and  Asia,  and  in 
crossing  arid  lowlands  in  their  way  to  the  sea  lose  a  large  part 
of  their  volume  by  evaporation.  Among  these  are  the  Missouri, 
Arkansas,  Red,  Colorado,  Columbia,  Euphrates,  Tigris,  Amu, 
Syr,  and  Indus.  The  rivers  of  southern  Europe  and  California 
belong  to  this  class,  and  being  small,  almost  run  dry  in  summer. 

In  desert  and  semi-arid  regions  the  streams  are  generally  intermittent 
or  occasional,  drying  up  a  part  of  every  year,  or  flowing  only  at  irregular 
intervals.     They  are  useful  only  for  irrigation. 

The  Savannah  River. —  Some  rivers  are  utilizable  for  all  pur- 
poses. The  Savannah  River,  between  Georgia  and  South  Caro- 
lina, is  an  example.  Although  the  total  length  of  its  basin  is 
only  250  miles,  it  traverses  three  distinct  belts, —  the  mountain, 
the  plateau,  and  the  plain. 

Its  headwaters  are  in  the  Blue  Ridge,  where  the  rainfall  is 
heavy,  the  slopes  are  steep,  and  there  are  many  falls  and  rapids. 
One  tributary,  the  Tallulah,  presents  a  succession  of  good  water- 
power  sites  for  thirty  miles,  ending  in  a  fall  of  400  feet  in  five 
miles.  This  region  should  be  wholly  devoted  to  the  growing 
of  hardwood  forests,  and  the  power  should  be  used  to  run  saw- 
mills and  other  machinery. 


THE  ECONOMIC  RELATIONS   OF  STREAMS 


105 


The  second  or  piedmont  belt  is  a  farming  region,  and  raises 
cotton.  A  group  of  reservoirs  located  at  the  foot  of  the  moun- 
tains would  prevent  floods,  store  water  for  use  during  the  low- 
water  periods,  and  help  in  furnishing  power  for  cotton  mills 
and  wood- working  factories.  At  the 
lower  edge  of  the  piedmont  plateau 
is  the  ''fall  Kne,"  where  the  river  de- 
scends an  escarpment  to  the  coastal 
plain.  The  power  here  has  made 
the  city  of  Augusta,  with  twenty - 
one  cotton  mills. 

From  Augusta  to  its  mouth, 
about  150  miles,  the  Savannah  is 
a  navigable  tidal  stream  flowing 
in  an  alluvial  valley.  With  its  flow 
properly  regulated,  there  would  be 
a  good  depth  of  water  all  the  year, 
and  the  harbor  of  Savannah  at  its 
mouth  would  be  one  of  the  best  in 
the  southern  states.  If  the  possi- 
bilities of  the  river  were  fully  util- 
ized, it  would  furnish  power,  cheap  transportation,  and  a  seaport 
for  a  rich  agricultural  and  manufacturing  community. 

The  Mississippi  System.  —  Any  one  looking  at  a  map  of  the 
United  States  would  be  impressed  with  the  importance  and 
advantages  of  the  Mississippi  River  system  which  drains  nearly 
half  the  country.  The  extreme  headwaters  on  the  west  rise 
in  the  Rocky  Mountains,  and,  flowing  through  narrow  valleys 
and  canons,  with  numerous  rapids  and  falls,  furnish  water  power 
and  opportunities  to  irrigate  the  dry  plains  below  (Figs.  60,  74, 
94).  The  eastern  tributaries  from  the  Appalachian  Mountains 
and  plateau  have  reached  a  later  stage  of  development,  and  their 
valleys  are  generally  mature  and  well  graded,  but  rather  narrow 
(Figs.  78,  95).  The  northern  sources  are  in  a  region  of  numer- 
ous lakes  which  act  as  reservoirs  and  help  to  equalize  the  flow 


Fig.  92.  —The  Savannah  River. 


io6 


PHYSICAL  GEOGRAPHY 


at  all  seasons.  The  branches  of  the  system  penetrate  nearly 
every  square  mile  of  the  interior  plain,  and  furnished  to  the 
canoe  of  the  Indian,  and  the  white  explorer  and  trader,  easy 
routes  of  travel.  The  early  settlement  of  the  "  Middle  West'' 
was  largely  accomplished  by  means  of  fiatboats  and  steamers,  and 
homesteads,  towns,  and  cities  were  located  along  the  streams, 
which  continued  to  be  the  chief  arteries  of  travel  and  trade  until 
the  advent  of  railroads  about  1850.  The  lower  Mississippi  was 
closed  to  commerce  during  the  Civil  War  (1861-65)  and  since 
that  time  its  use  for  transportation  has  rapidly  declined.  The 
Mississippi  system  on  the  map  appears  to  furnish  thousands  of 
miles  of  navigable  waterway,  but  it  has  proved  inadequate  to 
the  needs  of  to-day.  The  river  towns  which  are  still  prosperous 
and  growing  owe  more  to  the  railroads  than  to  the  river.  This 
condition  is  due  chiefly  to  natural  causes. 

Western  Tributaries.  —  The  Missouri  and  other  western  tributaries  north 
of  the  Red  River  receive  most  of  thsir  water  from  the  mountains,  and  in  cross- 
ing the  plains  traverse  a 
region  of  scant  rainfall. 
As  a  result  the  volume 
of  water  decreases  toward 
their  mouths  by  evapo- 
ration, and  they  are  over- 
loaded with  sediment. 
Their  channels  are  shal- 
low, crooked,  and  con- 
stantly shifting  by  the 
cutting  away  of  banks 
and  the  formation  of  bars. 
In  some  cases  the  river 
becomes  braided,  or  di- 
vided into  a  network  of  small  streams  which  spread  out  over  an  area  a  mile 
wide,  but  are  not  more  than  a  foot  deep.  In  the  dry  season  the  water  may 
disappear  from  the  surface,  and  the  stream  become  apparently  a  river  of 
sand.  The  volume  of  the  Missouri  varies  greatly  with  the  seasons.  The 
water  from  the  melting  snows  in  the  mountains  reaches  the  lower  river  in 
June,  when  the  volume  may  be  thirty  times  as  great  as  at  low  water  in 
November.    At  high  water  it  floods  a  wide  area  of  bottom  lands  and  scours 


FOO.T-H  ILL  SLOPES 


4^ 


ARABLE   B  O  T  T  O  M   L 


FOOT-HILL  SLOPES 


Fig.  93.  —  Braided  stream. 


THE   ECONOMIC   RELATIONS   OF   STREAMS  107 

out  its  channel  to  great  depths,  only  to  refill  it  as  the  current  slackens. 
The  Missouri  is  nominally  navigable  to  Fort  Benton,  but  navigation  has 
been  generally  abandoned.  Small  steamers  do  a  local  business  as  feeders  to 
the  various  railroads  which  cross  the  river. 


Fig.  94.  —  Bighorn  River  in  the  plains,  Wyoming.     Irrigation  canal  on  right  bank. 

The  upper  Mississippi  drains  a  country  of  moderate  rainfall 
and  is  not  subject  to  extreme  fluctuations  in  volume.  It  dis- 
charges nearly  as  much  water  as  the  Missouri,  and  is  navigated 
without  much  difficulty  as  far  as  St.  Paul. 

The  Ohio.  —  The  Ohio  basin  receives  a  heavier  rainfall  than 
any  other  part  of  the  Mississippi  system,  and  the  river  discharges 
three  fourths  as  much  water  as  the  Missouri  and  upper  Mississippi 
combined.  The  large  tributaries  are  not  overloaded  and  contain 
no  cataracts  and  few  rapids.  The  valleys  are  generally  narrow 
and  bordered  by  high  bluffs  (Figs.  78,  95).  The  streams  are  sub- 
ject to  excessive  fluctuations  of  volume.  The  rains  and  melting 
snows  of  spring  sometimes  raise  the  level  of  the  Ohio  at  Cincinnati 
seventy  feet  above  low-water  mark,  and  the  droughts  of  summer 
and  autumn  may  reduce  its  depth  to  three  feet.  On  a  river 
whose  level  varies  so  much  it  is  impossible  to  maintain  per- 
manent docks  and  landing  places,  the  water  front  of  towns  is 
liable  to  be  flooded  or  left  out  of  reach  by  boats,  and  navigation 


io8 


PHYSICAL  GEOGRAPHY 


is  inconvenient  and  dangerous.     In  spite  of  these  difficulties 
considerable  business  is  done  on  the  Ohio,  chiefly  in  transport- 


Fig-  05.  —  Ohio  River,  near  Madison,  Ind. 


ing  coal  from  Pennsylvania  in  barges,  which  are  lashed  together 
and  pushed  in  front  of  a  steamer.  The  United  States  govern- 
ment is  now  building  a  series  of  dams  in  the  Ohio  which  will 
maintain  a  depth  of  nine  feet  at  all  seasons. 


Fig.  96.  —  Ohio  River  barges  and  steamer.     Landing  place,  Evansville,  Ind. 

The  Lower  Mississippi.  —  The  lower  Mississippi,  from  the 
mouth  of  the  Ohio  to  the  Gulf,  flows  through  an  alluvial  valley 


THE  ECONOMIC  RELATIONS  OF  STREAMS 


109 


SCALE  OF  MILES 


M  I  S  S  O  U^^ 


J 

GULF       OF      M   E   X   I    C~6 


Fig.  97.  —  Lower  Mississippi  flood  plain.         Fig.  q8.  —  The  Mississippi,  near  Greenville, 

Miss.     The  heavy  lines   show   changes   in 
channel  in  12  years. 


no 


PHYSICAL  GEOGRAPHY 


25  to  80  miles  wide.  The  distance  in  a  direct  line  is  600  miles, 
but  by  the  course  oif  the  river  1,075  miles.  The  river  is  loaded 
with  the  mud  of  the  Missouri  and  other  western  tributaries,  and 
the  fall  is  less  than  six  inches  per  mile.  Consequently  the  main 
channel  is  extremely  tortuous  and  changeable. 

The  bank  on  the  outer  side  of  each  bend  and  on  the  up-valley  side  of 
each  tongue  of  land  is  rapidly  cut  away,  while  bars  are  built  on  the  op- 
posite sides.  Thus  the  river  continually  grows  more  crooked.  But  occa- 
sionally the  neck  of  land 
between  two  bends  be- 
comes so  narrow  that  ati 
high  water  the  river  cuts 
through  and  straightens 
itself.  The  new  cut-off, 
becomes  the  main  chan- 
nel, and  the  old  bend  is 
left  at  one  side  as  a  horse- 
shoe lake  (Fig.  98) .  Thus 
the  deep-water  channel, 
which  steamers  can  fol- 
low, is  constantly  shift- 
ing, and  does  not  remain 
in  the  same  place  from 
week  to  week.  Landing  places  must  be  moved,  and  even  town  sites  are 
washed  away  or  left  far  from  the  river.  The  lower  Mississippi  carries  the 
flood  waters  of  the  Missouri  and  Ohio,  which  sometimes  combine  to  increase 
its  volume  to  more  than  ten  times  its  low-water  volume.  It  rises  53  feet 
at  Cairo,  36  feet  at  Memphis,  48  feet  at  Helena,  53  feet  at  Vicksburg,  an4 
15  feet  at  New  Orleans.  Below  the  mouth  of  the  Red  the  rise  is  small 
because  the  surplus  water  is  carried  away  by  the  Atchafalaya  and  othei: 
distributaries.  In  the  natural  state  of  the  river  the  flood  waters  spread 
out  over  the  valley  floor,  and  finally  drain  off  through  the  bayous,  or  side 
channels,  to  the  main  stream  farther  down.  As  the  river  overflows  its 
banks  the  current  is  checked  rather  suddenly,  and  the  larger  and  coarser 
part  of  its  load  of  sediment  is  dropped  within  a  mile  or  two  of  the  channel. 
Thus  the  river  builds  up  its  own  banks  above  the  general  level  of  the  flood 
plain,  forming  natural  levees  (Fig.  99) .  The  floods  leave  a  thin  layer  of  fine 
and  fertile  mud  over  the  submerged  lands,  which  thus  acquire  a  soil  of  great 
and  frequently  renewed  fertility.  .  But  the  floods  are  destructive  to  prop- 


Fig.  99.  —  Natural  levee,  Wabash  River,  Ind. 


THE  ECONOMIC   RELATIONS   OF  STREAMS 


III 


erty,  and  render  the  utilization  of  such  lands  for  agriculture  difficult  and 
precarious. 

The  governments  of  the  United  States  and  of  the  various  states  con- 
cerned have  spent  many  millions  of  dollars  in  works  designed  to  prevent 
floods  and  to  improve  the  navigable  channel.     These  works  include  the 


Fig.  100.  — A  Mississippi  levee,  Greenville.     High  water  above  the  level  of  the  town. 

construction  of  reservoirs  at  the  sources  of  the  upper  Mississippi  to  store 
water  for  use  during  low  stages,  the  dredging  of  channels  across  bars,  and 
the  protection  of  banks  which  are  liable  to  be  cut  away.  But  the  most 
important  and  expensive  work  done  consists  in  the  building  of  artificial 
levees  or  embankments  of  earth,  which  are  now  completed  on  both  sides 
of  the  river  nearly  up  to  the  mouth  of  the  Ohio.  Confining  the  flood 
water  to  the  narrow  space 
between  the  levees  causes  it 
to  rise  higher  than  before, 
and  it  sometimes  runs  over 
or  breaks  through,  but  about 
three  fourths  of  the  alluvial 
valley  seems  to  be  effectu- 
ally protected  from  floods. 
Whether  the  confinement  of 
flood  waters  will  cause  the 
river  to  scour  out  and  deepen 
its  channel,  to  the  advantage  of  navigation,  remains  to  be  seen.  A  deep 
water  way  (fourteen  feet)  from  the  Great  Lakes  to  the  Gulf  is  greatly 
needed,  but  the  expense  of  construction  and  maintenance  would  perhaps 
be  too  great  for  even  so  rich  a  country  as  the  United  States. 


Fig.  loi.  —  Mississippi  steamer. 


112 


CHAPTER   VII 


GRADATION   BY   ICE 


While  running  water  is  the  most  effective  agent  in  modifying 
the  relief  of  the  land  surface,  many  important  features  are  due 
to  moving  ice.  On  high  mountains  and  in  polar  regions  at 
low  levels,  more  snow  falls  than  can  be  mxlted,  and  it  therefore 
accumulates  from  year  to  year.  A  bank  of  permanent  snow 
slowly  changes  by  thawing,  freezing,  and  pressure  into  solid  ice 
which  drains  away  down  the  slopes,  somewhat  as  water  does. 

Valley  or  Alpine  Glaciers.  —  A  valley  or  alpine  glacier  is  a 
stream  of  ice,  fed  by  a  snow  field  above  and  following  a  valley 


Fig.  103.  —Confluence  of  three  glaciers,  Switzerland. 


line  down  to  the  sea,  or  to  warmer  levels  where  it  is  melted  and 
changed  into  a  stream  of  water.  In  comparison  with  a  river, 
an  ice  stream  is  slow,  stiff,  and  awkward,  pro^ressiiig  only  a  few 
feet  a  year,  yet  it  accomplishes  great  results.     At  its  very  head 


113 


Fig.  104.  — A  cirque  in  the  Sierra  Nevada,  California.     (U.  S.  Bureau  of  Fisheries.) 


Bl              '<.^kj 

JKHk 

^^K^ . '  '*'  ^'iHBoi^ta 

^^^Hjj^^l 

^ig^^.^..-i,.f 

^^^^^^HUlBM9IHSr'^SM^^3BHUK^^?2^^^l 

,^.,^,--  ^^^i^^-^i^  \,  -, 


Fig.  105.  — Glaciated  valley,  Lauterbrunnen,  Switzerland. 

114 


GRADATION   BY  ICE 


"5 


Fig.  io6. 


Nunatak  Glacier,  Alaska,  discharging  bergs  into  a  fiord. 

Ice  divide  in  the  distance.     (U.S.G.S.) 


it  freezes  to  loose  rock  fragments  and  drags  them  away  from  the 
valley  walls  and  bottom.  Thus  a  semicircular  hollow  is  grad- 
ually eaten  into  the  mountain  side,  which  comes  to  resemble  a 
gigantic  armchair  and  is  called  a  cirque  (Figs.  104,  40).  Several 
glaciers  working  on  different  sides  may  reduce  the  mountain 
summit  to  a  thin,  sharp,  and  jagged  ridge.  Great  quantities  of 
dirt  and  stones  sUde  and  fall  from  the  steep  sides  of  the  valley 
upon  the  surface  of  the  ice  and  are  carried  downstream.  The 
ice  is  often  a  thousand  feet  or  more  in  thickness,  and  its  pres- 
sure on  the  valley  bottom  over  which  it  slides  amounts  to  many 
tons  per  square  foot.  The  sand,  gravel,  and  boulders  frozen  into 
the  under  surface  convert  the  glacier  into  a  powerful  rasp  which 
scratches,  rubs  down,  and  planes  off  the  bed  rock.  The  valley 
is  deepened  and  widened  into  a  rounded  shape,  like  the  letter 
U,  easily  distinguished  from  the  sharp  V-shaped  valley  of  a 
river  (Fig.  105). 

If  the  glacier  reaches  the  sea,  the  ice  breaks  off  in  large  chunks,  or  ice- 
bergs, which  drift  about  and  are  finally  melted.  In  most  cases  a  glacier 
is  brought  to  an  end  far  from  the  sea  by  melting,  and  the  whole  load  of 


ii6 


PHYSICAL  GEOGRAPHY 


1   wm 

r    ^^^(M^H 

#•• 

'^^1 

.-*            ^      -  V  .. 

"-^Hn^i      "^^^l^^^l 

^■we^^iiisap&^i;^^^."'^^^  • 

Fig.  107.  —  Glacial  drift,  Ontario  County,  N.  Y.     Boulders 
in  stream  have  been  washed  out  of  day  banks. 


loose  rock  which  it  carries 
is  left  in  a  heap  called  a 
terminal  moraine.  A  gla- 
cier can  carry  an  almost 
unlimited  load  of  sedi- 
ment, fine  or  coarse.  It 
carries  a  boulder  as  large 
as  a  house  as  easily  and 
rapidly  as  a  grain  of 
sand.  Therefore  it  has 
no  power  of  assorting  ma- 
terials, as  running  water 
has,  and  does  not  deposit 
them  in  layers.  Glacial 
drift  is  recognizable  as  a 
mixture  of  mantle  rock 
of    different    kinds    and 

sizes,  from  clay  as  fine  as  flour  to  boulders  weighing  many  tons,  all  mixed 

together  in  a  heap  or  spread  out 

in  a  sheet. 
A  valley  glacier  often  consists  ol 

a  trunk  stream  with  many  tribu- 
taries like   a   river  system.     The 

main  ice  stream  deepens  its  valley 

faster  than  the  weaker  tributaries 

can,  so  that  a  glaciated  valley  from 

which   the  ice  has  disappeared  is  _,.       o      r^    •  1  u    u     t  j- 

^^  Fig.  108.  — Glacial  boulder,  Indiana. 

characterized  by  numerous  water- 
falls, where  the  streams  from  the  "hanging"  tributary  valleys  cascade 

down  to  the  floor  of  the 
main  valley  (Figs.  84,  86, 
105).  In  an  old  glaci- 
ated mountain  system, 
such  as  that  of  Alaska, 
all  the  valleys  are  deeply 
filled  with  ice  which 
streams  from  the  divides 
and  snow  fields  in  various 
directions,  so  that  it  is 
possible    to    pass    easily 


Fig.  109.  —  Peaks  worn  down  to  snow  level,  Alaska. 


GRADATION   BY  ICE  1 17 

from  one  side  of  the  range  to  the  other  over  ice  divides  (Fig.  106).  The 
peaks  left  projecting  like  islands  above  the  snow  surface,  and  exposed  to 
severe  and  continuous  frost  action,  become  extremely  jagged  and  disin- 
tegrate down  to  snow  level,  which  thus  acts  as  a  base  level  of  erosion  (Fig. 
109).  Below  the  upper  limit  of  snow  the  rocks  are  protected  from  frost, 
but  exposed  to  the  abrasive  and  smoothing  action  of  moving  ice.  Thus  a 
valley  which  has  been  formerly  occupied  by  a  glacier  may  present  a  strik- 
ing contrast  between  the  smooth  and  polished  surface  of  its  lower  slopes 
and  the  rough  and  splintered  surface  above  (Figs.  102,  103). 

Valley  glaciers  and  glaciated  mountain  valleys  furnish  some 
of  the  most  impressive  and  fascinating  scenery  in  the  world. 
They  have  a  peculiar  charm  for  the  physiographer,  the  artist, 
and  the  adventurous  pedestrian  who  uses  the  ice  surface  as  a 
path  by  which  to  climb  the  peaks  or  cross  the  range. 

Ice  Caps. — An  ice  cap  is  a  mass  of  snow  and  ice  which  accu- 
mulates upon  a  plateau  and  moves  outward  in  all  directions,  as 
molasses  candy  spreads  out  on  a  plate.  Existing  ice  caps  vary 
in  dimensions  from  twenty  miles  in  diameter  in  Iceland  to  those 
of  Greenland  and  Antarctica,  where  an  area  larger  than  the 
United  States  is  completely  buried.  Fifty  thousand  or  a  hun- 
dred thousand  years  ago  North  America  north  of  40°  N.  Lat. 
and  Europe  north  of  50°  were  nearly  covered  by  a  succession  of 
ice  sheets  which  profoundly  modified  the  relief,  drainage,  and 
soil.  The  glaciated  area  may  be  roughly  .divided  into  two  con- 
trasted parts:  (i)  the  area  of  ice  accumulation  and  erosion,  cor- 
responding to  the  upper  and  middle  course  of  a  river;  (2)  the 
area  of  ice  destruction  and  drift  deposition,  corresponding  to 
the  flood  plain  and  delta  portion  of  a  river. 

American  Ice  Sheets.  —  In  America  the  snow  and  ice  accu- 
mulated on  the  Cordilleras  of  Canada  and  around  Hudson  Bay, 
and  extended  southward  to  the  Columbia,  Missouri,  and  Ohio 
rivers.  Near  the  centers  of  accumulation  the  ice  was  perhaps 
two  miles  thick,  and  in  moving  outward  it  swept  away  the 
mantle  rock,  wore  down  the  less  resistant  bed  rock,  and  left  a 
surface  of  peculiar  relief,  characterized  by  shallow  basins  and 
low,  rounded  hills,  with  no  regularity  in  shape  or  arrangement. 


ii8 


PHYSICAL  GEOGRAPHY 


The  basins,  filled  with  water,  constitute  the  innumerable  lakes 
which  cover  southern  Canada  with  tangled  chains  of  waterway. 
The  great  lakes  around  the  border  of  the  severely  glaciated 
area,  from  Ontario  to  Great  Bear,  owe  their  form,  size,  and  ex- 


^%^ 

^9-- 
% 


\V 


m>i<. 


-■-      ^   i^-r//y  1 1  i\^\\  \\\SX^^.-r:^  /ce  Center 


Fig.  110.  —  Ice  sheets  of  North  America. 


istence  largely  to  the  work  of  the  ice  sheets.  The  general  eleva- 
tion of  the  country  was  reduced  some  hundreds  or  perhaps 
thousands  of  feet,  and  the  bed  rock  was  left  bare  or  covered 
with  thin,  coarse  mantle  rock.  This  of  itself  renders  agriculture 
generally  impossible.  The  vegetation  growing  on  such  a  soil 
consists  of  coniferous  forest,  dense  and  of  great  value  for  timber 
in  favorable  localities,  thin  and  worthless  in  unfavorable.  On 
account  of  poor  drainage,  ''muskegs,"  or  marshes  covered  with 
mosses  and  shrubs,  are  numerous  and  extensive.  The  economic 
products  of  the  country  consist  almost  entirely  of  furs,  of  which 
it  furnishes  a  large  part  of  the  world's  supply.     Lumbering  is 


I 


GRADATION   BY   ICE 


119 


carried  on  in  those  parts  accessible  to  markets,  and  in  recent 
years  the  great  mineral  wealth  of  the  region  is  being  utilized. 


Fig.  III.  —  Laurentian  peneplain. 


The  Area  of  Glacial  Drift.  —  The  area  of  ice  destruction  and 
drift  deposition  lies  chiefly  south  and  west  of  the  chain  of  great 
lakes  in  northeastern  United  States  and  southern  Canada.  Here 
the  ice  was  relatively  thin  and  its  erosive  power  was  generally 


Fig.  112.  —  Terminal  moraine,  Sheboygan  County,  Wis. 

feeble.     In  melting  it  deposited  its  whole  load  of  mantle  rock 
in  a  continuous  sheet,  from  a  few  feet  to  several  hundred  feet 


120 


GRADATION   BY  ICE  121 

in  thickness.    The  bulk  of  the  drift  is  composed  of  boulder  clay, 
a  stiff  clay  containing  many  pebbles  and  boulders  of  various 


Fig.  114. -^Drumlin,  Macedon,  N.  Y.     (Partly  plowed.) 

sizes.  Generally  west  of  Pennsylvania  the  old  valleys  were 
filled  and  the  general  level  of  the  country  sHghtly  raised.  The 
surface  was  converted   into  a  smooth  plain  of  accumulation 


Fig.  115.  —  Esker,  Freeville,  N.  Y. 

(Figs.  34,  35),  varied  by  many  ridges  and  belts  of  hills  which 
mark  the  temporary  position  of  the  ice  edge.^     East  of  Ohio  the 

1  Glacial  drift  ridges  are: 

(i)  Marginal  moraines,  formed  by  an  accumulation  of  drift  along  the  edge  of 
the  melting  ice  sheet  (Figs.  45,  112). 

(2)  Karnes,  irregular  heaps  of  sediment  deposited  at  the  point  where  a  stream  of 
water  escaped  from  the  ice  margin  (Fig.  47). 

(3)  Esker s,  sharp  winding  ridges  of  sand  and  gravel  deposited  in  stream  chan- 
nels on  or  under  the  ice. 

(4)  Drumlins,  lenticular  or  prismatic  hills  of  clay,  formed  under  the  ice  at  some 
distance  back  from  its  edge. 


122 


PHYSICAL  GEOGRAPHY 


glacial  drift  was  too  thin  to  do  more  than  slightly  modify  the 
previous  rough  relief  of  the  country.     All  the  drainage  systems, 

^^  J — I  from  the  Columbia  to  the 
Ohio,  were  greatly  changed 
by  valley  filling,  damming, 
and  ponding,  displacement 
of  channels,  and  transfer- 
ence of  tributaries  from 
one  system  to  another. 

Economic   Relations.  — 

Of  more  importance  than 

these  changes  is  the  fact 

that  the  glacial  drift, 

^     «  , ..     *  *u  J  •**  u   X .      •   ,*        brought   from    the    north 

Fig.  ii6.  — Relation  of  the  drift  sheet  to  agriculture.  ° 

and  east  and  liberally 
spread  out  over  the  country  to  the  south  and  west,  constitutes 
a  rich,  deep,  and  enduring  soil,  which  makes  the  northern  states 


\ 


^0m:^.j;~^rmm0m:fJ 


Fig.  X17. — The  continental  glacier  of  Europe. 


GRADATION   BY   ICE  1^3 

and  southern  Canada  east  of  the  Rocky  Mountains  the  greatest 
food-producing  region  of  the  world,  and  one  of  the  most  densely 
populated  parts  of  North  America.  This  region  also  owes  to 
the  ice  sheets  the  most  important  inland  waterway  in  the 
world,  the  Laurentian  Great  Lakes.  The  states  heavily  coated 
with  glacial  drift  have  a  population  of  about  thirty  millions,  or 
forty-five  to  the  square  mile.  The  states  south  of  the  glacial 
boundary  have  a  population  of  about  twenty-seven  millions,  or 
thirty-two  to  the  square  mile. 

European  Ice  Sheets.  —  In  Europe  the  main  region  of  ice  accumulation 
was  in  Scandinavia  and  Finland,  and  the  region  of  ice  destruction  and  drift 
deposit  in  central  Russia  and  north  Germany.  The  same  contrasts  between 
the  two  in  relief,  drainage,  and  soil  are  found  as  in  North  America.  Scandi- 
navia and  Finland  form  a  country  of  lakes  and  forests  with  a  very  small 
area  of  arable  land,  while  Germany  and  central  Russia  are  rich  agricultural 
states.  The  European  glacial  drift  is  not  generally  so  heavy  or  so  pro- 
ductive as  the  American,  and  lying  in  higher  latitudes  has  not  influenced 
products  and  population  to  any  such  extent. 


CHAPTER  VIII 


STANDING   WATER 


Lakes,  Ponds,  and  Marshes.  —  Lakes,  ponds,  and  marshes  are 
bodies  of  standing  water  which  occupy  depressions  in  the  land 
surface.  Lake  basins  are  due  to  a  variety  of  causes.  The 
largest  basins  have  been  produced  by  the  warping  or  breaking 
of  the  earth  crust  by  internal  forces.  In  some  cases  these  basins 
are  so  large  that  the  excess  of  rainfall  over  evaporation  is  in- 
sufficient to  fill  them,  and  the  lake  has 
no  outlet.  Salts  brought  by  streams  in 
solution  accumulate,  and  the  water  be- 
comes a  brine.  Of  such  lakes  the  Caspian 
Sea  is  the  largest  and  the  Dead  Sea  the 
lowest,  1,300  feet  below  sea  level.  The 
Great  Basin  in  western  United  States 
contains  many  lakes,  of  which  Great 
Salt  Lake  in  Utah  is  the  largest.  They 
are  all  subject  to  fluctuations  of  level 
and  area,  according  to  the  seasons,  or 
the  periodic  variations  of  rainfall.  Many 
of  the  smaller  ones  are  temporary,  con- 
taining water  for  a  few  days  or  months, 
or  lasting  for  a  year  or  two  before  they 
dry  up.  Most  of  the  lakes  of  central 
Africa  lie  in  the  course  of  the  great  rift 
valley  (p.  64).  Some  of  them  have 
Fig.  118.— East  African  lakes  no  outlct,  but  the  great  lakcs  Nyassa, 
va  ey.  Tanganyika,    and    Victoria    are    sources 

of  the  Zambezi,  Kongo,  and  Nile.     The  great  lakes  of  North 
America  lie  along  the  southwestern  border  of  the  Laurentian 

peneplain  (p.  45),  from  New  York  nearly  to  the  Arctic  Ocean. 

124 


STANDING  WATER 


125 


Their  basins  are  due  primarily  to  warping  and  stream  erosion, 
but  have  been  considerably  modified  by  glacial  action.  On 
account  of  their  size  and  location,  the  Laurentian  lakes  are  of 
special  importance.  Lakes  Superior,  Michigan,  Huron,  Erie, 
and  Ontario  form  the  largest  connected  body  of  fresh  water  on 
the  globe.  Their  form  and  relative  positions  suggest  that  their 
basins  are  parts  of  an  old  river  valley  which  has  been  divided 
by  a  series  of  dams.  Their  great  depth,  extending  in  all  except 
Lake  Erie  below  sea  level,  may  be  due  to  glacial  erosion. 

During  the  retreat  of  the  North  American  ice  sheet  and  subsequently  the 
Laurentian  lakes  were  subjected  to  many  changes  of  form,  area,  and  outlet. 
Their  waters  at  different  periods  overflowed  through  the  upper  Mississippi, 
the  Illinois,  the  Wabash,  the  Ottawa,  and  the  Mohawk  (Fig.  113).  Their 
former  outlets  at  Chicago,  Fort  W^ayne,  Ind.,  Rome,  N.  Y.,  and  Nipis- 
sing,  Canada,  furnish  easy  routes  for  canals  and  railroads.  Lake  Winnipeg  is 
a  shrunken  remnant  of  Lake  Agassiz,  which,  held  in  by  an  ice  dam  on 
the  north,  once  covered  110,000  square  miles  in  Canada,  Minnesota,  and 
North  Dakota,  and  emptied  through  the  Minnesota  River.  The  sediment 
deposited  upon  its  bottom  now  forms  the  soil  of  the  famous  wheat  fields  of 
the  Red  River  region. 

Glacial  Lakes. — Lakes  are  nowhere  else  so  numerous  as  in  the 
regions  formerly  covered  by  the  North  American  and  European 
ice  sheets,  as  large- 
scale  maps  of  Canada, 
northeastern  United 
States,  Sweden,  and 
Finland  will  show. 
Glacial  lake  basins 
are  hollows  in  bed 
rock  eroded  by  mov- 
ing ice,  or  hollows 
made  by  irregular 
deposition    of    drift. 

-_  ,  Fig.  119.  —  Glacial  lake,  Derwentwater,  England. 

Many  are  partly  or 

wholly  due  to  drift  dams  in  the  course  of  a  stream.     Some  are 

kettleholes  left  by  the  melting  of  detached  blocks  of  ice  (Fig.  48). 


126 


PHYSICAL  GEOGRAPHY 


The  courses  of  terminal  moraines  are  generally  marked  by 
thousands  of  small  lakes,  as  may  be  seen  in  Indiana,  Michigan, 
Wisconsin,  Minnesota,  and  northern  Russia  and  Germany. 

Alpine  Lakes.  —  Long,  narrow,  and  very  deep  lake  basins  which  occur 
in  mountain  regions,  and  are  hence  called  alpine  lakes,  are  characteristic 


Fig.  120.  —  Glacial  lake,  Lima,  N.  Y. 
Esker  in  left  margin. 


Fig.  121.  —  Alpine  lake,  Lugano. 


results  of  ice  work.  The  Italian,  Swiss,  and  Scotch  lakes  and  Lake  Chelan 
in  Washington  belong  to  this  class  and  are  unrivaled  for  scientific  interest 
and  for  grand  and  picturesque  scenery.  The  Finger  Lakes  of  New  York, 
on  the  northern  slope  of  the  Appalachian  plateau,  are  of  similar  but  less 
extreme  character,  and  are  probably  due  to  similar  causes. 


Fig.  122.  — Finger  lake:  Hemlock  Lake,  N.  Y. 
Valley  is  13  miles  long,  half  a  mile  wide  and  1,000  feet  deep. 


STANDING  WATER 


127 


Volcanic  Lakes.  —  Lakes  are  in  some  cases  due  to  the  damming  of  a 
stream  valley  by  a  flow  of  lava  from  a  volcano.  Old  volcanic  craters  some- 
times fill  with  water,  forming 
lakes  of  which  Crater  Lake, 
in  southern  Oregon,  is  a 
famous  example.  It  is  five 
miles  in  diameter  and  bounded 
by  precipitous  cliffs  from  500 
to  2,200  feet  high.  The  water 
is  2,000  feet  deep. 

Life  History  of  Lakes. 

—  In  arid  regions,  where 

the  rainfall  is  insufficient    Fig.  123.- 

to  equal  the  water  lost 

by  evaporation,  the  lakes  have  no  outlet  and  are  salt.     They 

often  dry  up,  leaving  beds  of  salt,  soda,  borax,  and  other  valu- 


Model  of  the  basin  of  Crater  Lake,  Oregon. 
(U.S.G.S.) 


Copyright  by  Doubleday,  Page  &  Co. 

Fig.  124. — Lake  filling  with  vegetation. 


(Fletcher's  Soils.) 


able  minerals.  In  regions  of  abundant  rainfall  lakes  overflow  at 
the  lowest  point  of  the  basin  rim.  As  the  outlet  stream  cuts  its 
channel  deeper,  the  water  is  drained  away  and  the  lake  level  is 


128  PHYSICAL   GEOGRAPHY 

lowered.  This  process  is  often  hastened  by  cutting  an  artificial 
ditch  which  may  drain  the  lake  completely,  leaving  rich  agri- 
cultural land.  At  the  same  time  inlet  streams  are  filling  up  the 
basin  with  sediment  and  will  in  time  convert  it  into  a  lacustrine 
plain.  Therefore  lakes  are  among  the  most  short-lived  of  natu- 
ral features  and  are  always  relatively  young. 

In  the  case  of  small,  shallow  lakes,  their  destruction  is  hastened  by  the 
growth  of  vegetation.  Aquatic  plants,  which  absorb  the  greater  bulk  of 
their  food  from  the  air,  grow  and  decay  year  after  year,  until  the  basin  is 
filled  with  vegetable  matter  and  the  lake  is  converted  into  a  marsh,  peat 
bog,  or  wet  meadow.  Some  lake  basins  fill  with  marl,  which  is  valuable  as 
a  fertilizer  and  for  making  cement. 

Economic  Relations.  —  Lakes  act  as  reservoirs  which  regulate 
the  flow  of  outlet  streams  and  prevent  both  floods  and  extreme 
stages  of  low  water.  They  are  also  settling  basins  for  sedi- 
ment, so  that  a  stream  flowing  out  of  a  lake  is  usually  clear. 
The  Niagara  and  St.  Lawrence  rivers  are  striking  examples  of 
streams  which  are  clear  and  subject  to  slight  changes  of  volume. 
Large  lakes  furnish  the  best  of  inland  waterways  (p.  loo).  The 
smaller  ones  are  sources  of  food  supply  and  add  greatly  to  the 
variety  and  beauty  of  landscape.  Lakes  are  everywhere  favorite 
summer  resorts,  which  attract  thousands  of  people  who  find 
pleasure  and  recreation  in  camping,  boating,  fishing,  and  bath- 
ing. The  "  Chautauqua,"  or  summer  assembly  for  religious, 
educational,  social,  and  sanitary  purposes,  takes  its  name  from 
Lake  Chautauqua  in  New  York. 

Gradation  by  Standing  Water.  —  Seas  and  lakes  are  bodies  of 
standing  water  but  not  of  still  water.  Their  waters  have  no 
general  and  continuous  movement  in  one  direction,  as  a  stream 
has,  but  under  the  influence  of  the  wind  and  the  moon  are 
agitated  by  waves,  currents,  and  tides.  These  movements 
accomplish  their  most  important  work  along  the  margin  where 
land  and  water  meet,  and  produce  a  characteristic  series  of 
coast  forms.  These  may  be  found  in  miniature  along  the  shore 
of  almost  any  small  lake  or  pond. 


STANDING  WATER 


129 


Beaches  and  Bars.  —  Where  the  coast  land  is  low  and  the 
coast  waters  are  shallow  the  waves  build  up  a  ridge  of  sand  or 
gravel  which  is  as  high  as  the 
highest  storm  waves  can  lift 
the  material.  Behind  this 
heach  there  is  generally  a  strip 
of  shallow  water  called  a 
lagoon.  A  harrier  heach  is  a 
long,  continuous  ridge  some 
distance  off  shore  (Fig.  28). 
Where  the  shore  line  is  in- 
dented by  a  bay  the  beach 

is    often    extended    across    its       pi^.  ,,5.  _  Beaches  and  lagoons.  CayugaUke. 

mouth,    forming   a   hay  bar. 

A  bar  built  out  from  shore  into  deeper  water  is  called  a  spit, 

and  if  bent  back  at  the  end,  a  hook.     Barrier  beaches  and  bars, 


Cape  Cod 


Fig.  126.— The  end  of  Cape  Cod,  Massachusetts.    Two  hooked  spits. 

as  the  names  imply,  render  a  coast  difficult  of  access  from  the 
water  and  form  serious  obstructions  to  commerce.  The  lagoons, 
inlets,  and  bay  mouths  are  usually  too  shallow  to  admit  vessels 


130  PHYSICAL  GEOGRAPHY 

of  considerable  size.  Where  the  tides  are  high  and  strong  enough 
to  keep  the  inlets  scoured  out,  good  harbors  are  found.  On  a 
low,  sandy  coast  wind  and  waves  work  together  and  dunes  are 
combined  with  beaches. 

The  Gulf  and  Atlantic  coasts  of  the  United  States  south  of  Cape  Cod 
present  perhaps  the  longest  stretch  of  barrier  beach  coast  in  the  world. 
On  the  coast  of  Texas  the  beach  extends  100  miles  without  a  break.  Gal- 
veston and  other  bays  are  rendered  inaccessible  except  by  artificial  channels. 
The  keys  and  reefs  of  Florida  are  peculiar  in  being  partly  the  work  of  coral 
animals.  Along  the  coast  of  Georgia  and  South  Carolina  the  tides  are  strong 
enough  to  break  up  the  beach  into  the  so-called  "  sea  islands,"  and  the 
numerous  deep  inlets  lead  to  good  harbors.  From  Charleston  to  New  York 
the  coast  is  bordered  by  a  nearly  continuous  beach,  which  sweeps  in  long, 
gentle  curves  from  point  to  point.  Behind  it  is  a  belt  of  lagoons  and  tidal 
marshes,  expanding  in  North  Carolina  into  shallow  sounds.  This  coast 
belt  is  interrupted  by  the  drowned  valleys  of  the  Chesapeake,  Delaware,  and 
Hudson,  which  let  deep  tide  water  and  the  largest  vessels  far  into  the  in- 
terior. The  beaches  of  New  Jersey  and  Long  Island  are  popular  summer 
resorts.  Railroads  have  been  built  to  and  along  them,  and  towns  and 
cities  have  sprung  up,  with  hotels  and  places  of  entertainment  for  visitors, 
who  come  by  the  hundred  thousand  to  enjoy  the  sea  breezes  and  the  bath- 
ing (Fig.  28). 

Sea  Cliffs.  —  Where  the  coast  land  is  high  and  the  coast 
waters  are  deep,  the  waves  pound  against  the  shore  with  tre- 
mendous force  and  undercut 
it  into  a  vertical  cliff.  The 
fragments  are  rolled  over, 
ground  up,  and  carried  away 
by  the  undertow,  or  backrush 
of  water  along  the  bottom. 
The  result  of  this  is  a  plat- 
form or  terrace  a  little  below 

Fig.  i27.-Sea  cliff.  Lake  Erie.  ^^^      j^^^j^     ^^^^^^     ^^^     -^^^^ 

solid  rock,  partly  built  of  mantle  rock,  and  bordered  by  a  con- 
stantly retreating  cHff.  The  character  of  a  cUlf  coast  varies 
with  the  kind  of  rock.  If  the  rock  is  of  uniform  hardness  and 
without  joints  or  seams,  the  cHff  is  smooth  and  unbroken,  like 


I 


STANDING  WATER 


131 


the  chalk  cliffs  of  England  and  France  and  the  clay  cliffs  of 
Lake  Michigan  (Fig.  35).  Such  a  coast  may  be  entirely  without 
indentations  or  har- 
bors. If  the  rock  is 
complex  in  material 
and  structure,  the 
waves  soon  eat  away 
the  weak  places  and 
leave  the  more  resist- 
ant masses  standing 
out  as  promontories 
and  islands  (Fig.  43). 
Small  isolated  masses 
of  rock  along  the 
shore  are  called  sker- 
ries in  Norway  and 
stacks  in  Scotland.  Such  a  coast  may  be  extremely  jagged  and 
dangerous  to  shipping,  while  at  the  same  time  it  offers  numer- 
ous coves  where  small  boats  may  find  shelter  and  concealment. 
Economic  Relations.  —  On  the  whole,  the  general  result  of 
the  work  of  standing  water  is  to  cut  the  bordering  lands  down 
to  its  own  level  and  to  surround  itself  with  barriers  which  make 
access  to  the  land  more  difficult.  If  it  were  not  for  the  power 
of  running  water  and  ice  to  break  through  the  barriers,  ocean 
and  lake  commerce  would  be  much  more  restricted  than  it  is. 


W-*-' 

"^^■■i^^^^H 

■Ml^^ien 

Fig,  128.  —Chalk  cliffs,  France.    Arch  and  stack. 


CHAPTER  IX 

GRADATION  BY   GROUND   WATER  AND   WIND 

The  Ground  Sea.  —  A  large  part  of  the  rainfall  sinks  into  the 
ground  and  penetrates  the  earth  crust  to  great  but  unknown 
depths.  The  ground  water  may  be  thought  of  as  forming  a  sea 
many  miles  in  depth  and  extending  through  the  rock  sphere 

beneath  the  land  surface  from 
ocean  to  ocean.  Thus  the 
water  sphere  is  really  contin- 
uous around  the  globe.  The 
upper  surface  of  the  ground 
sea,  called  the  water  table,  is 
not  level,  but  is  roughly  par- 
allel with  the  surface  of  the 
land.  In  lakes,  marshes,  and 
streams  the  water  table  stands 
at  the  surface  of  the  ground. 
In  regions  of  small  rainfall  it 
may  He  a  thousand  feet  or 
more  below  the  surface.  The 
level  of  the  water  table  is  not 
constant  at  the  same  locality, 
rising  during  a  wet  season  and 
sinking  during  a  dry  season. 
The  water  of  the  ground  sea 
is  seldom  at  rest.  In  com- 
pact rocks  the  movement  is  very  slow,  in  porous  rocks  more 
rapid,  and  in  rocks  traversed  by  open  joints  and  cracks  there 
is  a  circulation  in  streams  comparable  to  that  on  the  land 
surface. 


Fig.  129. 


■Section  of  fissured  rock  and  well. 

(U.S.G.S.) 


132 


GRADATION  BY  GROUND  WATER 


133 


Fig.  130. — Hot  spring  4eposits,  Algeria. 


Work  of  Ground  Water.  —  Most  of  the  minerals  of  the  earth 
crust  are  more  or  less  soluble,  and  as  the  ground  water  penetrates 
more  deeply  it  be- 
comes more  highly 
charged  with  them. 
Its  temperature  also 
increases  with  the 
depth,  and  the  lower 
parts  of  the  ground 
sea  are  probably  com- 
posed of  hot  water 
saltier  than  the  ocean . 

In  many  places  the  deep  ground  water  rises   to  the   surface, 
forming  mineral  springs.     These  waters  contain  gases,  sulphur, 

iron,  and  various  salts 
in  solution,  which  ren- 
der them  of  value  in 
the  treatment  of 
disease. 

Hot  Springs,  Ark.,  and 
Saratoga  Springs,  N.  Y., 
are  famous  health  resorts, 
and  there  are  hundreds 
of  similar  character  in  all 
parts  of  the  world.  In 
old  volcanic  regions  the 
earth  crust  is  hot  near 
the  surface,  and  steam 
generated  in  subterra- 
nean conduits  throws  out 
columns  of  hot  water, 
forming  geysers,  or  spout- 
ing springs.  The  geysers 
of  the  Yellowstone  Park 
are  unsurpassed  in  num- 
ber, variety,  and  size.  As 
Fig.  131.— Old  Faithful  geyser,  Yellowstone  Park.  hot    ground    water    rises 


134 


PHYSICAL  GEOGRAPHY 


Fig.  132.  — Mouth  of  cave,  Indiana. 

Roof  of  stream  channel  fallen  in. 


toward  the  surface  the  pressure  upon  it  diminishes,  it  cools  and  deposits 
the  minerals  held  in  solution,  eventually  filling  the  passage.  In  this  way 
ores  of  gold,  silver,  and  other  metals  are  concentrated  and  placed  within 
reach  of  the  miner. 

Limestone  is  a  very  soluble  rock,  and  in  some  limestone  regions 
the   earth   crust  is  honeycombed   with   underground   drainage 

channels,  leaving  few 
streams  on  the  sur- 
face. Some  of  the 
channels  have  been 
enlarged  by  solution 
and  the  falling  in  of 
the  roof  to  a  diame- 
ter of  hundreds  of 
feet  and  a  length  of 
many  miles.  Most 
of  the  great  caves  of 
the  world  are  in  lime- 
stone rock,  among  them  Mammoth  Cave  in  Kentucky,  and 
Wyandotte  Cave  in  Indiana. 

Economic  Relations.  —  Ground  water  is  everywhere  a  common 
source  of  water  supply  for  domestic  use.  The  outflow  of  natural 
springs  is  sometimes  large  and  of  good  quality,  but  the  main 
dependence  is  upon  wells.  If  a  hole  is  sunk  into  the  ground  to 
a  point  below  the  water  table,  it  will  fill  up  to  that  level  with 
water.  In  shallow  wells  the  largest  supply  is  obtained  from 
strata  of  sand  and  gravel.  Such  wells,  especially  in  towns,  are 
unsafe  for  domestic  use,  on  account  of  pollution  by  drainage 
from  cesspools,  sewers,  barnyards,  and  other  sources  of  filth. 
The  clearest  and  most  agreeable  well  water  may  be  the  most 
dangerous.     Deep  wells  are  less  liable  to  contamination. 

In  some  cases  water  flows  from  a  well  without  pumping,  or  even  spouts' 
into  the  air  like  a  fountain.  Very  deep  flowing  wells  are  called  artesian. 
The  water  of  a  flowing  well  comes  from  a  porous  stratum  which  outcrops  I 
on  the  surface  somewhere  at  a  higher  level  than  the  mouth  of  the  welLj 
The  outcrop  and  source  of  supply  may  be  hundreds  of  miles  from  the  well.] 


GRADATION   BY  GROUND   WATER  AND   WIND 


135 


Over  a  large  area  of  the  plains  east  of  the  Rocky  Mountains  artesian  wells 
are  common,  some  of  which  furnish  water  enough  to  irrigate  a  hundred- 
acre  farm.    The  water  comes  from  thick  strata  of  porous  sandstone  which 


^^ 


QOOOFT.^O^^^^'' 


HORIZONTAL  SCALE 

20       _^        20  60  MILES 


Fig.  133.  —  Cross  section  from  Rocky  Mountains  across  Nebraska.  Dakota  sandstone  under 
Pierre  clay  carries  water  from  Rocky  Mountains  and  supplies  artesian  wells  on  the  plains.  Note 
nearly  horizontal  strata  of  plains  turned  up  against  granite  core  of  the  mountains.     (U.S.G.S.) 

underKe  the  plains  at  considerable  depths.  The  sandstone  outcrops  along 
the  foothills  of  the  mountains,  where  it  absorbs  the  rainfall  and  transmits 
the  water  eastward.  Whenever  a  well  penetrates  the  overlying  strata  and 
reaches  the  sandstone,  water  rises  to  the  surface. 

Ground  water  plays  an  im- 
portant part  in  the  work  of 
gradation  by  extending  the 
processes  of  weathering  and 
rock  decay  to  great  depths, 
and  by  promoting  chemical 
changes  and  transporting  ma- 
terial in  the  earth  crust. 

Work  of  Wind. — Wherever 
fine,  dry  mantle  rock  is  ex- 
posed without  a  cover  of  veg- 
etation the  wind  is  able  to 
transport  it  in  almost  unlim- 
ited quantities.  As  in  the 
case  of  running  water,  both 
the  quantity  and  the  coarse- 
ness of  sediment  which  run- 
ning air  is  able  to  carry 
increase  in  a  high  ratio  to  the  velocity,  but  air  is  so  much  less 
dense  than  water  that  its  sediment  is  generally  limited  to  dust 
and  sand.     Only  tornadoes  are  capable  of  lifting  pebbles  and 


Fig.  134.  — Artesian  well,  North  Dakota. 


136  PHYSICAL  GEOGRAPHY 

boulders.  The  wind  is  therefore  a  delicate  assorting  agent,  and 
its  dej)osits  may  usually  he  recognized  by  the  fact  that  they 
have  been  thoroughly  winnowed.  Unlike  running  water,  air 
moves  in  broad  sheets  and  carries  material  as  freely  up  a  slope 
as  down.  There  is  a  strongly  marked  rhythm  in  its  motion, 
and  its  effects  are  a  combination  of  those  of  currents  and  waves. 

One  fourth  of  the  land  surface  of  the  globe  has  less  than  ten 
inches  of  annual  rainfall,  and  in  such  areas  outside  the  polar 
regions  wind  action  is  generally  more  important  than  other 
processes.  Rocks,  subjected  to  great  daily  changes  of  tem- 
perature, crumble  rapidly.  The  lighter  mineral  particles,  like 
mica,  are  carried  away  by  the  wind,  and  quartz  grains  are  left 
as  sand.  The  sand  itself  is  blown  about  and  acts  as  a  power- 
ful erosive  agent,  undercutting  cliffs  and  enlarging  valleys.  In 
general,  mantle  rock  accumulates,  and  hollows  at  all  elevations 
are  filled.  Some  of  it  is  transported  entirely  outside  the  desert 
region.  A  wind-worn  surface  is  much  less  varied  than  a  water- 
worn  surface.  While  running  water  cannot  erode  below  the 
level  of  the  sea  or  of  the  lake  into  which  it  flows,  there  is  no 
definite  downward  limit  to  wind  erosion.  Its  tendency  is  to 
produce  a  stony  peneplain  with  projecting  knobs  of  hard  rock 
and  belts  of  drifting  sand  dunes  (Fig.  37).  When  the  surface  is 
reduced  below  sea  level,  the  sea  is  liable  to  overflow  it  and  stop 
the  process.  The  margin  of  the  desert  is  indefinite  and  fluctu- 
ating. Its  sands  often  encroach  upon  neighboring  cultivated 
areas  unless  stopped  by  human  agency. 

Dunes.  —  A  tornado  in  the  desert  may  raise  a  sand  column 
or  spout  many  hundred  feet  and  sustain  it  as  long  as  the  whirl 
of  air  continues,  finally  dropping  it  over  the  surrounding  country, 
but  the  ordinary  winds  seldom  lift  sand  more  than  a  few  feet. 
A  slight  lull  causes  most  of  it  to  be  dropped,  and  it  accumu- 
lates in  the  lee  of  any  obstruction,  as  snow  is  drifted  behind  a 
fence.  The  pile  of  sand  itself  forms  an  obstruction  beyond  which 
more  sand  accumulates,  and  the  drift  or  dune  grows  to  be  a  hill 
with  a  long,  gentle  slope  on  the  windward  side  and  a  steep  slope 


GRADATION   BY  WIND 


137 


on  the  leeward  side.    The  wind  blows  the  sand  up  the  long 
slope  and  drops  it  in  the  eddy  beyond.     Thus  the  pile  becomes  a 


Fig.  135.      Dunes,  Algeria. 

"marching  dune  "  which  slowly  advances,  burying  forests,  build- 
ings, or  whatever  lies  in  its  way.  In  the  course  of  years  the  dune 
may  move  on  far  enough  to  uncover  what  it  previously  buried. 

Coast  Dunes.  —  The  margins  of  seas,  lakes,  and  retreating  ice  sheets 
arc  generally  bare  of  vegetation,  and  present  conditions  favorable  for  wind 
action.  Low  windward 
coasts  are  often  bordered 
by  belts  of  drifting  dunes, 
as  in  Holland,  Germany, 
France,  the  Atlantic  coast 
of  the  United  States,  and 
the  east  and  south  shores 
of  Lake  Michigan.  The 
dunes  form  a  barrier 
which  protects  the  land 
from  storm  waves  and 
high  tides,  but  also  makes 
commerce  difficult  (Fig. 
28).  In  France  the  prog- 
ress of  the  dunes  inland 
has  been  stayed  by  the  planting  of  pine  trees.  Moving  sand  is  very  un- 
favorable for  the  growth  of  vegetation,  and  forms  the  ground  of  nearly 


Fig.  136.  —Dunes  near  coast  of  North  Carolina. 


138  PHYSICAL  GEOGRAPHY 

absolute  desert.  Sand  dunes  are  among  the  most  destructive  agents  in 
nature,  and  can  be  controlled  only  where  some  kind  of  vegetation  can  be 
made  to  grow  upon  them  and  hold  them  down. 

Dust.  —  Very  fine  dust  ejected  from  volcanoes  to  a  height  of 
many  miles  has  remained  in  the  air  for  months,  and  even  years, 
before  settling,  and  has  been  carried  around  the  world.  The 
snow  fields  in  the  interior  of  Greenland,  far  from  any  exposed 
ground,  are  covered  with  fine  dust,  which  may  settle  upon  it 
from  extraterrestrial  space.  Dust  from  the  Sahara  is  some- 
times carried  by  the  wind  to  northern  Germany. 


CHAPTER  X 


SOILS 


The  loose  rock  material  in  which  plants  take  root  and  find 
food  is  called  soil.  Practically  the  whole  vegetative  covering 
of  the  land,  and  consequently  all  animal  and  hmnan  as  well  as 
plant  life,  depend  upon  the  soil  for  existence.  Soils  are  por- 
tions of  mantle  rock  and  have  been  formed  by  the  physical  and 
chemical  disintegration  of  bed  rock  by  the  agents  and  processes 
of  weathering  (p.  72).  They  may  be  thought  of  as  "rock 
meal,"  or  "rock  flour." 

Sedentary  Soils.  —  Soils  are  at  first  sedentary  or  residual^ 
that  is,  formed  by  the  decay  of  the  bed  rock  which  lies  under 
them,  and  vary  according 
to  the  kind  of  rock  from 
which  they  are  formed. 
Sedentary  soils  are  usu- 
ally thin,  but  may  accu- 
mulate to  the  depth  of 
some  hundreds  of  feet. 
They  contain  undecom- 
posed  fragments  of  bed 
rock,  which  increase  in 
number  and  size  down- 
ward. 

Igneous  rocks  differ  so  widely 
in  composition  and  texture 
that  they  weather  into  a  great  variety  of  soils,  from  very  poor  to  very  rich. 
Granite  and  gneiss  often  crumble  at  first  into  a  barren  gravel  like  that 
of  the  English  moors.  Chemical  changes  finally  reduce  the  quartz  to 
sand,  and  the  feldspar  and  mica  to  clay,  the  latter  being  decomposed  very 
slowly.    The  fertility  of  granitic  soils  is  roughly  proportional  to  the  amount 

139 


Fig.  137. — Residtial  gravel,  Texas. 


140 


PHYSICAL  GEOGRAPHY 


Fig.  138.  —  Residual  clay  on  shale,  Indiana. 


of  feldspar  present,  quartz 
and  mica  being  distinctly  un- 
favorable. Lava  soils  vary- 
in  their  rate  of  weathering 
and  fertility  with  their  chem- 
ical composition. 

Limestone  soils  are  famous 
for  fertility,  as  in  the  blue- 
grass  region  of  Kentucky  and 
the  prairies  of  Texas.  The 
lime  is  dissolved  and  washed 
awayj  and  the  soil  consists 
largely  of  the  residue  of  insol- 
uble impurities.  Sandstones 
weather  into  sandy  soils  which 
are  generally  poor,  but  may 
be  productive  from  the  pres- 
ence in  the  rock  of  other  ingredients  acting  as  a  cement.  Shale  weathers 
into  clay,  which,  if  not  too  fine  and  compact,  makes  a  good  soil.  Conglom- 
erate weathers  into  gravel,  which 
is  apt  to  be  very  barren. 


Colluvial  Soils.  —  On  mod- 
erate or  steep  slopes  the 
native  soil  creeps  slowly 
downward  by  the  action  of 
gravity,  frost,  and  rain  wash, 
and  in  arid  regions  sometimes 
accumulates  in  valleys  be- 
tween the  mountains  to  a 
depth  of  several  thousand 
feet.  Such  slowly  moving 
soil  masses  are  called  colluvial: 

Transported  Soils.  —  The 
surface  of  plains,  valleys,  and 
lowlands  is  generally  covered 
with  soil  which  has  been 
brought   down    from    higher 


Fig.  139. — Colluvial  soil  near  Crawfordsville,  Ind. 
The  surface  material  creeps  faster  than  that  at  a 
slight  depth,  tipping  the  trees. 


142  PHYSICAL  GEOGRAPHY 

levels  by  water,  ice,  or  wind.     Transported  soils  are  generally 
rich  because  they  are  derived  from  many  kinds  of  rocks  and 


Copyright  by  Doubleday,  Page  &  Co. 
Fig.  141,  —  Eolian  soil,  "  Palouse  Country  "  of  Oregon  and  Washington.     (Fletcher's  Soils.) 

contain  a  mixture  of  minerals  which  is  likely  to  include  all  kinds 
of  plant  food. 

Alluvial  soils  are  deposited  by  streams  on  flood  plains,  "  bot- 
tom lands,"  and  deltas,  and  are  well  known  as  exceedingly  pro- 
ductive. Their  productiveness  is  due  to  the  variety  of  elements 
of  which  they  are  composed,  to  the  fineness  of  division,  and 
to  their  frequent  renewal  by  deposits  from  flood  waters.  Great 
flood  plains  and  deltas,  such  as  those  of  the  Nile,  Hoang, 
Ganges,  Rhine,  and  Po,  have  produced  great  crops  for  thou- 
sands of  years  and  will  continue  to  do  so  in  future.  The  allu- 
vial valley  of  the  Mississippi  and  its  tributaries  is  of  the  same 
character,  but  is  not  yet  fully  utilized  (Fig.  97). 

Glacial  soils  are  the  deposits  from  melting  ice  sheets  (p.  122) 
and  are  more  variable  than  alluvial  soils,  but  generally  not  far 
behind  them  in  productiveness.  Glacial  or  boulder  clay  con- 
tains a  great  variety  of  minerals,  finely  ground  and  intimately 


SOILS  143 

mixed,  and  when  it  includes  enough  of  sand  and  gravel  to  make 
it  pervious  and  workable  it  is  extremely  rich  and  enduring. 
The  glacial  drift  of  the  United  States  is  one  of  the  most  valuable 
food-producing  areas  in  the  world  (Figs.  113,  116,  117). 

Eolian  soils  are  deposited  by  the  wind  and  are  fine  and  sandy. 
Since  they  occur  mostly  in  arid  regions,  where  plant  food  is  not 
washed  out  by  rains,  they  retain  the  elements  of  fertility  much 
better  than  the  sands  of  humid  regions.  On  desert  sands,  when 
wetted  by  sHght  rainfall,  vegetation  springs  up  at  once,  and  if 
kept  moist  by  irrigation  becomes  remarkably  luxuriant. 

Physical  Composition  of  Soils.  —  Physically  soils  consist  of 
clay,  silt,  sand,  gravel,  pebbles,  and  humus. 

Clay  is  an  extremely  fine,  soft  powder  produced  by  the  chemical 
decomposition  of  various  minerals,  of  which  feldspar  is  the  most 
important.  It  consists  of  thin,  rounded  scales  from  2  3" 0^0  00  to 
^oVo^  C)f  an  inch  in  diameter.  When  wet,  clay  swells  up  into 
a  sticky,  plastic  substance  which  shrinks  in  drying  to  a  tough, 
coherent  mass.  It  is  very  retentive  of  water,  gases,  and  minerals 
in  solution  and  presents  such  a  large  surface  for  the  plant  rootlets 
to  work  upon  that  clay  soils  are  "strong."  At  the  same  time 
clay  acts  as  a  cement  which  holds  other  ingredients  together 
and  renders  soil  difficult  to  till. 

Silt  and  sand  are  rock  powders  produced  by  the  mechanical 
pulverization  of  various  minerals,  of  which  quartz  is  by  far 
the  most  abundant.  Common  sand  consists  almost  entirely  of 
quartz  crystals  more  or  less  rounded.  If  the  crystals  are  un- 
worn and  angular,  the  sand  is  ''  sharp."  The  diameter  of  silt 
grains  is  from  5^o^o  0  to  5^0  ^f  an  inch,  that  of  sand  grains  from 
5  0  0  to  2V  o^  ^^  ii^ch,  but  even  the  finest  silt  can  be  recognized 
by  its  harsh,  gritty  feel  between  the  fingers  or  teeth.  Pure  silt 
or  sand  is  incoherent  and  easily  worked,  but  does  not  retain 
moisture  well,  and  is  less  fertile  than  clay. 

Gravel  is  composed  of  generally  hard,  rounded  grains  or  pebbles 
from  2V  ^^  an  inch  up  to  2  or  3  inches  in  diameter,  and  is  looser 
and  more  permeable  than  sand. 


144  PHYSICAL  GEOGRAPHY 

Humus  is  a  loose,  black  mold  produced  by  the  partial  decay 
of  vegetable  matter,  and  is  an  essential  ingredient  of  all  good 
soils. 

Types  of  Soils.  —  The  common  types  of  agricultural  soils  are 
classified  as  follows: 


Sandy  soils  contain 

80  %  sand, 

10  %  clay. 

Sandy  loams     " 

60-70%     " 

10-25%      " 

Loam  soils        " 

40-60%      '' 

15-30%     " 

Clay  loams       " 

10-35%      '' 

30-50%      " 

Clay  soils 

10%      " 

60-90  %      " 

Gravelly  and  stony  loams  contain  gravel  and  pebbles  and  are 
common  in  regions  covered  with  glacial  drift. 

Peat  and  muck  soils  are  formed  by  the  decay  of  vegetation 
in  shallow  lakes,  ponds,  and  swamps.  Some  clay  and  silt  are 
blown  in  by  the  wind  and  carried  in  by  streams.  They  contain 
from  30  to  nearly  100  per  cent  of  humus.  If  the  vegetable 
matter  is  sufficiently  decayed  and  is  mixed  with  considerable 
mineral  matter,  good  drainage  renders  such  soils  productive. 

Loess  soils  are  peculiar  deposits  consisting  of  a  mixture  of  silt  and  clay 
laid  down  partly  by  wind  and  partly  by  water,  and  are  generally  very  produc- 
tive. They  cover  extensive  areas  along  the  borders  of  the  glacial  drift  in  the 
United  States  and  Europe.  The  loess  of  China  is  an  eolian  deposit  blown 
from  the  central  plateaus  and  is  in  some  places  1,000  feet  thick  (Fig.  142). 

Adobe  soils  are  peculiar  to  semi-arid  regions  and  common  in  south- 
western United  States.  They  are  very  sticky  when  wet,  and  hard  when 
dry,  but  are  unusually  rich  in  plant  food. 

Alkali  soils  are  common  in  arid  regions.  They  contain  large  quantities 
of  common  salt,  carbonate  and  sulphate  of  soda,  and  other  compounds 
which  are  brought  to  the  surface  in  solution  and  left  by  evaporation  of  the 
water  as  a  whitish  or  black  crust.  Few  plants  will  grow  in  such  soils,  but 
they  can  be  improved  by  irrigation  and  drainage,  which  wash  out  the  salts. 

Tropical  Soils.  —  The  high  temperature  of  tropical  regions 
favors  rapid  decomposition  of  soil  ingredients  and  hastens  all 
chemical  changes.  The  luxuriance  of  tropical  vegetation  is  not 
wholly  due  to  the  heat  and  moisture  of  the  air,  but  also  to  the 
fertility  of  the  soil,  which  is  therefore  in  part  responsible  for 


SOILS 


US 


Fig.  142.  — Loess  deposits,  eroded,  China. 

the  easy-going  and  indolent  ways  of  tropical  people.  Tropical 
soils  are  exceptionally  rich  in  humus,  but  plant  food  is  rapidly 
leached  out  by  the  heavy  rains.  They  are  often  of  a  deep-red 
color  due  to  the  diffusion  of  iron  oxide.  The  red  clay  soils 
produced  by  the  weathering  of  volcanic  rocks  are  called  laterite 
(brick  earth).     The  name  is  often  applied  to  any  red  soil. 

Chemical  Constituents  of  Good  Soil.  —  For  plant  growth  at 
least  seven  chemical  elements  must  be  present  in  the  soil  in 
soluble  form,  —  nitrogen,  potash,  phosphorus,  lime,  iron,  mag- 
nesium, and  sulphur.     The  last  three  are  usually  present  in  such 


146  PHYSICAL  GEOGRAPHY 

abundance  as  to  require  no  attention,  but  the  first  four  are  sure 
to  be  exhausted  by  continuous  cropping  and  must  be  suppHed 
artificially.  Therefore,  nitrogen,  potash,  phosphorus,  and  lime 
are  the  essential  ingredients  of  all  fertiHzers.  The  total  quantity 
needed  is  relatively  small  because  plants  obtain  about  90  per 
cent  of  their  substance  from  the  carbon  and  oxygen  of  the  air. 

Soils  contain  air  and  other  gases  which  are  necessary  to  plant  life.  The 
roots  of  most  plants  need  air  to  breathe,  and  for  farm  crops  the  soil  should 
be  well  ventilated  by  tillage  and  underdraining.  The  presence  of  air 
hastens  the  chemical  processes  which  render  plant  food  available,  and  thus 
increases  fertility. 

Plants  as  Soil  Makers.  —Plants  perform  a  very  important 
work  in  soil-making.  Two  years  after  an  eruption  of  Krakatao, 
a  volcano  in  Sunda  Strait,  which  destroyed  all  vegetation,  the 
surface  of  the  lava  was  found  to  be  slimy  with  microscopic 
plant  fife,  active  in  breaking  down  silicates  into  clay,  combining 
elements,  and  preparing  soil  for  higher  plants.  Most  soils 
swarm  with  bacteria,  fungi,  molds,  and  algae  which  literally  eat 
the  rocks,  and  by  living  upon  mineral  matter  produce  humus. 
They  flourish  best  in  warm,  moist,  well- ventilated  soils,  where 
they  hasten  the  decay  of  vegetable  matter.  Some  are  injurious, 
but  most  of  them  are  harmless  and  many  are  beneficial.  It  has 
been  said  that  the  soil  is  not  primarily  a  medium  on  which  to 
grow  herbs  and  trees,  but  a  domain  created  by  the  activities 
of  low  forms  of  life  for  their  own  benefit,  and  that  the  higher 
plants  exist  by  virtue  of  these,  just  as  animals  live  by  virtue  of 
the  herbage. 

Temperature  of  the  Soil.  —  The  temperature  of  the  soil  is  as 
important  for  plant  growth  as  that  of  the  air  above  it.  Few 
seeds  will  germinate  if  the  soil  temperature  is  below  45  degrees, 
and  65  to  100  degrees  is  most  favorable.  Gravelly  and  sandy 
soils  are  warmer  than  clay.  Wet  soils  are  cold  because  much 
of  the  heat  received  from  the  sun  is  used  up  in  evaporating 
water;  consequently  soils  are  warmed  by  drainage.  Lands 
which  slope  toward  the  sun  are  warmer  than  those  sloping  away 


SOILS  147 

from  it,  and  dark-colored  soils  absorb  more  heat  than  light-colored. 
The  temperature  of  the  soil  is  raised  by  the  fermentation  and 
decay  of  vegetable  and  animal  matter. 

Soil  Water.  —  All  fertile  soils  contain  large  quantities  of  water. 
The  free  or  ground  water  fills  the  spaces  between  the  particles 
up  to  the  level  of  the  water  table  (p.  132).  The  depth  of  the 
water  table  may  generally  be  determined  by  the  height  at  which 
water  stands  in  surface  wells.  If  the  water  table  stands  too 
near  the  surface,  the  plant  roots  may  be  drowned  and  the  soil 
is  of  Httle  valye  until  it  is  drained. 

Above  the  water  table  the  surface  of  each  soil  grain  is  covered 
by  a  thin  film  of  water  which  sticks  to  it  and  supplies  the  plant 
roots  with  food.  The  driest  road  dust  contains  some  film 
water,  and  a  good  soil  may  hold  more  than  half  its  weight.  Film 
water  is  mostly  derived  from  the  free  water  below,  but  a  little 
may  be  absorbed  from  the  air.  Film  water  is  constantly  rising 
from  the  water  table  and  evaporating  from  the  surface  of  the 
ground.     Thus  plants  are  kept  alive  through  a  dry  season. 

The  water  contains  salts  in  solution  which  are  left  by  evaporation, 
forming  a  surface  crust.  It  is  often  important  to  conserve  the  film  water 
by  checking  evaporation.  This  may  be  done  by  tillage,  which  pulverizes 
the  crust,  or  by  covering  the  surface  with  a  mulch  of  vegetable  matter  or 
even  of  fine  dust.  The  finer  the  soil  the  more  surface  the  particles  present 
for  film  water  and  the  plant  food  it  contains.  Therefore  "  fineness  is  rich- 
ness." A  good  soil  may  contain  from  250  to  450  billion  particles  per  ounce, 
and  the  aggregate  surface  of  all  the  particles  in  one  cubic  foot  may  meas- 
ure from  one  to  four  acres. 

The  Hfe  and  growth  of  plants  require  a  very  large  quantity 
of  water,  which  they  obtain  entirely  from  the  soil.  Average 
farm  crops  use  from  300  to  400  tons  of  water  per  acre.  Plant 
roots  absorb  food  only  when  it  is  dissolved  in  soil  water,  and 
the  solution  is  so  weak  that  to  get  food  enough  they  must  use 
great  quantities  of  water,  most  of  which  escapes  by  evaporation 
through  the  leaves.  Under  ordinary  conditions,  production  is 
almost  directly  proportional  to  the  water  supply  during  the 
growing  season.     Including  losses  by  run-off  and  evaporation 


148 


PHYSICAL  GEOGRAPHY 


from  the  soil,  a  rainfall  of  from  5  to  25  inches  just  before  and 
during  the  growing  season  is  necessary  to  produce  farm  crops. 
In  middle  latitudes  the  rainfall  of  autumn  and  winter  is  of 
little  benefit  to  the  farmer,  who  must  depend  upon  the  rains  of 
spring  and  early  summer. 

Irrigation  does  not  add  anything  to  the  actual  quantity  of 
water  on  the  land,  but  utilizes  for  crop  growing  water  which  would 
naturally  evaporate  or  run  off  to  the  sea.  Water  is  obtained 
from  lakes,  streams,  and  wells,  and  is  distributed  over  the  fields  at 
times  and  in  quantities  which  can  be  regulated  according  to  the 
needs  of  the  crop  (Figs.  36,  60,  90,  94).  The  product  per  acre  of 
irrigated  lands  far  exceeds  that  of  lands  naturally  supplied  with 
water,  but  the  area  of  lands  which  can  be  irrigated  is  relatively 
very  small.     Irrigated  lands  in  India  aggregate  25  million  acres, 

in  Egypt  6  milHon,  in 
Italy  3.7  milHon,  and 
in  the  United  States 
10.5  million .  The  area 
in  the  United  States 
which  may  possibly 
be  irrigated  is  esti- 
mated at  75  milUon 
acres,  which  is  less 
than  one-tenth  of  the 
total  arid  region. 

The  Conservation 
of  Soils.  —  Soil  is  es- 
pecially subject  to  ero- 
sion, and  is  carried 
away  by  every  stream, 
to  be  finally  deposited 
in  the  sea.  In  some 
places  the  soil  is  liable 
to  removal  by  the  wind.  A  covering  of  vegetation,  especially  a 
forest,  largely  prevents  the  washing  away  of  soil.     On  forested 


Fig.  143. — SoU  wash  and  gullying,  North  Carolina. 


SOILS  149 

slopes  the  cutting  of  the  trees  is  often  followed  by  rapid  gully- 
ing and  destruction  of  the  land  for  any  useful  purpose,  while 
the  valleys  below  suffer  almost  as  much  from  excess  of  mantle 
rock  brought  down  and  deposited.  In  old  countries  a  series  of 
''  breaks  "  or  dams  is  sometimes  built  across  the  valley  to  stop 
the  waste  of  soil.  All  such  regions  are  more  valuable  if  kept  in 
forest,  which  can  be  thinned  out  at  intervals  and  renewed  by 
planting.  Many  species  of  grass,  sedge,  rush,  willows,  and  other 
plants  which  form  a  dense  network  of  roots  are  useful  as  soil 
binders. 

Soil  and  Population.  —  The  population  which  any  given 
region,  or  the  world  as  a  whole,  can  support  is  strictly  Hmited 
by  the  amount  of  water  available  for  crops.  This  is  as  true 
in  humid  as  in  arid  regions.  Notwithstanding  the  large  pro- 
portion of  the  face  of  the  earth  occupied  by  water,  less  than 
half  the  land  surface  has  sufficient  rainfall  to  support  a  moder- 
ately dense  population,  and  one  third  of  it  is  either  frozen  or 
too  dry  for  agriculture.  As  long  as  men  depended  chiefly  upon 
agriculture  for  a  Hving,  population  was  necessarily  most  dense 
on  fertile  and  easily  cultivated  soils,  and  these  were  generally 
alluvial.  To-day  the  density  of  population  is  greatest  in  manu- 
facturing regions,  where  the  character  of  the  soil  is  of  no  im- 
portance. Facihties  for  transportation  are  so  great  that  food 
and  clothing  may  be  supplied  from  distant  lands,  and  the  best 
agricultural  regions  have  a  relatively  sparse  or  medium  popu- 
lation. In  the  most  advanced  industrial  countries,  like  the 
United  States,  the  population  of  purely  agricultural  counties  and 
states  has  remained  stationary,  or  has  grown  actually  smaller 
for  several  decades.  This  is  due  to  improvements  in  farm 
machinery,  which  enable  one  man  now  to  do  the  work  done  by 
four  or  five  men  fifty  years  ago. 


CHAPTER  XI 

THE    SEA 

The  sea  is  a  continuous  body  of  salt  water  which  covers  about 
72  per  cent  of  the  surface  of  the  earth  crust.  The  average  depth 
of  the  sea  is  a  little  over  two  miles,  and  its  greatest  about  six 
miles.  Its  depth  in  proportion  to  its  area  would  be  like  that  of 
a  lake  three  miles  wide  and  one  to  six  feet  deep,  and  would  be 
represented  on  a  seven-foot  globe  by  a  film  of  water  from  one 
twentieth  to  one  third  of  an  inch  thick.  The  relative  shallow- 
ness of  the  ocean  basins  is  of  importance  from  the  fact  that 
they  are  not  deep  enough  to  hold  all  the  water,  which  conse- 
quently spreads  over  the  low  margins  of  the  continental  plat- 
form and  covers  more  than  one  sixth  of  it  (p.  24).  The  sea 
surrounds  four  great  land  masses  and  thousands  of  islands,  and 
is  divided  into  five  great  oceans  (Figs.  16,  17,  18,  150). 

The  Oceans.  —  The  Southern  Ocean  forms  a  continuous  belt 
around  the  earth  south  of  40°  S.  Lat.,  and  is  a  means  of  com- 
munication between  the  other  oceans  which  open  into  it.  It  is 
about  1,600  miles  wide,  comprises  about  one  fifth  of  the  sea  area, 
and  is  more  than  two  miles  deep. 

The  Pacific  Ocean  comprises  about  40  per  cent  of  the  sea  area, 
or  nearly  30  per  cent  of  the  face  of  the  earth.  It  is  roughly 
circular  in  outline,  with  a  diameter  of  about  10,000  miles,  and 
is  nearly  surrounded  by  land  except  on  the  south.  Its  bed  is 
broken  by  numerous  ridges  which  bear  upon  their  crests  thou- 
sands of  small  islands.  It  also  contains  many  holes  where  the 
water  is  five  or  six  miles  deep. 

The  Atlantic  Ocean  is  9,000  miles  long,  and  between  Africa 
and  South  America  only  1,700  miles  wide.  Its  greatest  depths 
are  from  four  to  five  miles.     It  forms  a  broad  channel  of  com- 

150 


THE   SEA  151 

munication  between  the  north  and  south  polar  waters.  It  com- 
prises about  one  fourth  of  the  sea  area. 

The  Indian  Ocean  has  been  called  "  half  an  ocean  "  because 
it  extends  northward  only  to  the  tropic  of  Cancer.  Its  area  is 
about  one  eighth  of  the  whole  sea,  and  its  average  depth  is  over 
two  miles. 

The  Arctic  Ocean  is  smaU  and  nearly  inclosed  by  land  at  about 
70°  N.  Lat.  An  opening  1,200  miles  wide  between  Norway  and 
Greenland  connects  it  with  the  north  Atlantic.  A  large  part  of 
it  is  covered  with  drifting  ice,  and  its  depths  are  Uttle  known. 
Soundings  by  Nansen  north  of  Eurasia  and  by  Peary  at  the 
pole  show  that  it  is  more  than  9,000  feet  deep. 

Sea  Water.  —  The  sea  water  contains  about  3 J  per  cent  of 
mineral  matter  in  solution,  more  than  three  fourths  of  which  is 
common  salt.  Most  of  this  mineral  matter  has  probably  been 
brought  by  rivers  from  the  land.  While  sea  water  contains 
minute  quantities  of  almost  every  known  element,  more  than 
97  per  cent  of  the  dissolved  matter  consists  of  salts  of  soda, 
magnesia,  and  lime.  The  gases  of  the  atmosphere  penetrate  the 
sea  in  varying  proportions  to  the  bottom.  The  quantity  of 
oxygen  diminishes  and  that  of  carbon  dioxide  increases  with 
increasing  depth. 

Temperature.  — The  temperature  of  the  surface  water  of  the 
sea  is  between  30°  and  40°  F.  near  the  poles  and  between  70° 
and  90°  near  the  equator  (Fig.  150).  The  temperature  of  the 
deep  bottom  water  varies  from  29°  in  the  polar  regions  to  35° 
under  the  equator. 

The  layer  of  water  warmer  than  40°  is  nowhere  more  than  4,800  feet 
deep,  and  generally  much  less.  Eighty  per  cent  of  all  the  water  in  the 
sea  has  a  temperature  below  40°.  This  is  due  to  the  fact  that  the  heat  of 
the  sun  does  not  penetrate  the  water  more  than  about  600  feet,  and  to 
the  creep  of  the  cold  bottom  water  of  the  Southern  Ocean  into  the  Pacific, 
Atlantic,  and  Indian,  crowding  the  warmer  equatorial  waters  upward. 
Owing  to  many  physical  causes  the  temperature  of  the  sea  is  more  constant 
than  that  of  the  land,  the  seasonal  change  being  seldom  more  than  10  or  20 
degrees.    Lands  swept  by  winds  from  the  sea  have  an  oceanic  climate 


152  PHYSICAL  GEOGRAPHY 

marked  by .  relatively  small  differences  of  temperature  between  summer 
and  winter. 

Pressure  and  Density.  —  The  pressure  of  sea  water  is  equal  in  all  direc- 
tions and  increases  at  the  rate  of  more  than  one  ton  per  square  inch  for 
every  mile  of  depth.  The  density  varies  with  the  temperature,  pressure, 
and  quantity  of  salts  in  solution.  The  density  of  the  surface  water  is 
greatest  in  tropical  regions  of  small  rainfall  and  rapid  evaporation,  and 
least  in  the  equatorial  regions  of  heavy  rainfall  and  the  polar  regions  of 
freezing  and  melting  ice. 

Waves.  —  Waves  are  usually  produced  by  the  friction  of  the 
wind.  They  present  a  series  of  parallel  or  irregular  ridges  and 
hollows  which  follow  one  another  across  the  surface  of  the  water. 
They  are  very  superficial,  seldom  disturbing  the  water  to  a 
depth  greater  than  ibo  feet.  Each  wave  appears  to  consist  of 
a  ridge  or  mound  of  water  moving  forward  with  the  wind,  but 


Fig.  144. — Breakers. 

in  the  open  sea  the  water  really  moves  up  and  down  in  a  circular 
or  elliptical  path.  A  field  of  standing  grain  in  the  wind  or  a 
cloth  shaken  up  and  down  may  be  thrown  into  similar  waves. 
Waves  10  or  15  feet  high  lift  and  drop  a  vessel  about  ten 
times  a  minute.  Storm  waves  sometimes  reach  a  height  of 
50  feet  and  travel  60  miles  an  hour,  passing  a  given  point  at  the 
rate  of  about  four  a  minute.  In  shallow  water  the  front  slope 
of  the  wave  becomes  steeper  and  the  crest  higher,  until  finally 


THE   SEA  153 

it  falls  forward  and  breaks,  rolling  over  and  over  like  a  barrel. 
On  a  shelving  shore  such  breakers  may  reach  a  height  of  100  feet 
or  more,  and  hurl  forward  many  tons  of  water,  striking  blows 
like  a  hammer  and  pounding  cHffs,  breakwaters,  and  Hghthouses 
to  pieces.  The  undertow,  or  backward  rush  of  the  water  along 
the  sea  bottom,  is  efficient  in  grinding  up  and  removing  rock 
fragments. 

Waves  are  the  principal  agents  in  breaking  down  the  seaward  margin  of 
the  land  and  in  building  beaches,  bars,  and  spits  (p.  129).  Their  effects 
are  on  the  whole  unfavorable  to  man  by  rendering  navigation  more  difficult 
and  dangerous  and  the  coasts  of  the  land  less  accessible.  Shipwrecks  are 
generally  caused  by  waves.  Mariners  sometimes  succeed  in  calming  the 
sea  and  making  a  space  of  relatively  smooth  water  around  a  ship  by  pour- 
ing overboard  a  quantity  of  oil.  The  floating  oil  so  reduces  the  friction  of 
the  wind  upon  the  surface  of  the  water  that  wave  motion  nearly  ceases. 

Tides.  —  The  level  of  the  sea  is  subject  to  a  regular,  periodic 
rise  and  fall  which  is  called  the  tide.  It  varies  in  amount  at 
different  places.  On  the  deep,  open  ocean  it  is  probably  less 
than  one  foot.  On  the  coasts  of  oceanic  islands  it  is  not  more 
than  six  or  seven  feet,  while  at  the  heads  of  funnel-shaped  inlets, 
such  as  the  Bay  of  Fundy,  it  amounts  to  as  much  as  fifty  feet.  If 
we  should  watch  the  tide  from  any  point  along  the  coast  at  low 
water,  we  should  see  the  rocks,  bars,  and  portions  of  the  beach 
and  sea  bottom  laid  bare ;  then  the  water  would  slowly  flow  or 
creep  up  for  several  hours  and  cover  them.  High  water  would 
be  followed  by  an  ehh  or  fall,  lasting  six  hours  or  more.  The 
interval  between  two  periods  of  high  water  or  low  water  is 
twelve  hours  and  twenty-six  minutes,  but  it  is  not  always  equally 
divided  between  ebb  and  flow,  the  rise  being  generally  more  rapid 
than  the  fall. 

The  difference  of  level  between  high  and  low  water  varies  not  only  at 
different  places  but  at  different  times  at  the  same  place.  These  phenomena 
must  have  been  observed  by  all  peoples  who  have  lived  along  the  shore  of 
the  sea,  and  it  must  have  been  noticed  at  a  very  early  period  that  the  times 
of  high  and  low  water  have  some  relation  to  the  position  and  phases  of 
the  moon.  The  connection  between  the  moon  and  the  tides  was  not  un- 
derstood, however,  until  Newton's  discovery  of  the  law  of  gravitation. 


154 


PHYSICAL  GEOGRAPHY 


If  the  earth  were  a  globe  of  water,  it  is  easy  to  understand 
how  the  attraction  of  the  moon  would  draw  it  out  of  shape  and 


Fig.  145.  — High  tide,  North  Haven,  Maine. 

produce  a  sKght  elongation  in  the  direction  of  a  line  connecting 
the  earth  and  moon.  The  effect  upon  th6  spheroidal  shell  of 
sea  water  is  the  same  as  though  it  were  a  complete  sphere. 


Fig.  146.  — Low  tide,  North  Haven,  Maine. 


If  the  moon  were  always  above  the  same  point  on  the  earth, 
there  would  always  be  high  water  at  that  point,  the  moon  would 
cause  no  change  in  the  level  of  the  sea  anywhere,  and  conse- 
quently there  would  be  no  lunar,  tides;  but  as  the  earth  rotates 


THE   SEA  155 

on  its  axis  from  west  to  east,  the  point  directly  under  the  moon 
and  the  other  points  of  high  and  low  water  travel  around  the 
earth  from  east  to  west  at  the  same  rate  as  the  apparent  motion 
of  the  moon. 

Thus  every  part  of  the  sea  has  two  stages  of  high  water  and  two  of  low 
water  within  the  time  between  two  transits  of  the  moon  over  any  given 
place  (24  hours  and  52  minutes).  The  period  is  more  than  twenty-four 
hours,  because  the  moon  is  actually  moving  in  its  orbit  eastward  in  the 

tIBSTI       ;-QUARTER 

I  Neap,  Tide  \ 


FULL 

0- 

MOON 

"-'■© 

Spring 
fice 

NEW 
MOON 

\ 
\ 

Neap'Jide 

/ 

1 

f 

THIRD/'     "NQUARTER 

Fig.  147. 

same  direction  as  the  rotation  of  the  earth,  and  after  one  rotation  of  the 
earth  on  its  axis,  it  takes  fifty-two  minutes  for  any  given  point  on  the  earth 
to  overtake  the  moon. 

The  sun  also  produces  tides  in  the  sea  in  the  same  manner  as  the  moon, 
but  on  account  of  its  greater  distance  the  solar  tides  are  much  smaller  than 
the  lunar.  At  new  moon  and  full  moon  the  sun,  earth,  and  moon  are  all 
in  the  same  straight  line,  as  shown  in  Fig.  147,  and  the  lunar  and  solar 
tides  combine  to  produce  a  greater  rise  and  fall  than  usual,  called  spring 
tide.  At  intermediate  periods  the  sun  and  moon  act  at  right  angles  to 
each  other  and  produce  a  smaller  rise  and  fall  than  usual,  called  neap 
tide. 

The  increased  rise  of  the  tide  in  shallow  water  near  shore,  in  river  mouths, 
and  in  wide-mouthed  indentations  of  the  coast  enables  large  vessels  to  pene- 
trate the  land.  The  inward  movement  of  water  during  a  rising  tide  gives 
sufficient  depth  and  a  favorable  current  for  ingoing  vessels,  and  the  out- 
ward flow  during  a  falling  tide  is  favorable  for  outgoing  vessels.  These 
conditions  are  especially  important  on  coasts  where  the  continental  shelf 
is  wide,  and  in  estuaries  and  drowned  valleys  like  those  of  eastern  United 
States,  the  British  Isles,  France,  the  Netherlands,  and  Germany. 


156  PHYSICAL  GEOGRAPHY 

Currents.  —  Under  the  influence  of  the  prevailing  winds  the 
surface  waters  of  the  sea  are  driven  in  wide,  shallow  streams, 
or  currents,  from  shore  to  shore.  Deflected  by -the  land  masses, 
they  perform  great  circuits  in  the  ocean  basins  on  each  side  of 
the  equator.  The  map  on  pages  1 60-1 61  shows  the  location  and 
direction  of  the  principal  ocean  currents.  What  may  be  called 
the  trunk  streams  are  the  north  and  south  equatorial  currents, 
which,  under  the  influence  of  the  trade  winds  (Figs.  170,  171, 
172),  flow  westward  in  broad  belts  and  are  turned  northward 
and  southward  by  the  eastern  shores  of  the  continents.  Helped 
on  by  the  prevaiHng  westerly  winds,  they  recross  the  oceans  in 
middle  latitudes,  and,  returning  toward  the  equator  on  western 
shores,  complete  the  circuits.  The  eddy  in  the  north  Atlantic 
is  joined  by  a  large  branch  from  the  south  equatorial  current 
and  attains  exceptional  speed,  depth,  and  temperature  off  the 
coast  of  Florida,  where  it  is  called  the  Gulf  Stream.  This  cur- 
rent loses  velocity  and  depth,  and,  north  of  40°  N.  Lat.,  spreads 
out  into  a  sheet  of  warm  surface  water  which  drifts  at  the  rate 
of  a  mile  or  so  a  day  far  into  the  Arctic  Ocean. 

This  large  body  of  warm  water  in  the  north  Atlantic  raises  the  tempera- 
ture of  the  winds  which  blow  over  it  and  contributes  to  the  mildness  and 
humidity  of  climate  in  western  Europe.  The  water  returns  from  the 
Arctic  Ocean  southward  along  the  east  coast  of  Greenland  and  Labrador, 
forming  a  reversed  eddy  of  cold  water. 

In  the  north  Pacific  the  Japan  Current,  or  Kurosiwo,  behaves  in  a  similar 
manner. 

In  middle  southern  latitudes  the  circuit  in  each  ocean  is  partly 
merged  into  the  west  wind  drift,  which  circulates  eastward 
around  the  earth  in  the  Southern  Ocean.  In  the  northern  part 
of  the  Indian  Ocean  the  direction  of  circulation  is  reversed  in 
winter  by  the  northeast  monsoons  (Fig.  150). 

As  a  general  rule  between  40°  N.  Lat.  and  40°  S.  Lat.  the  currents  brinj 
relatively  warm  water  to  the  eastern  coasts  of  the  continents  and  relatively] 
cool  water  to  the  western  coasts.     In  higher  latitudes  this  rule  is  reversed.] 
By  this  circulation  of  waters  the  temperatures  of  the  oceans  are  parti] 
equalized,  and,  through  the  influence  of  the  water  upon  the  temperature  of 


THE    SEA 


157 


1  he  winds  blowing  over  it,  the  climate  of  the  continents  is  greatly  modified. 
The  most  notable  effects,  due  in  part  to  the  ocean  currents,  are  the  mild 
winter  temperatures  and  heavy  rainfall  of  western  Europe  and  northwestern 
North  America,  and  the  cool  summers  of  northeastern  North  America  and 
Asia  and  southwestern  South  America. 

Ocean  currents  bring  food  supply  to  fixed  marine  animals  such  as  the 
coral  polyps,  which  flourish  best  in  the  strong,  warm  equatorial  currents, 
and  also  to  fish  which  swarm  in  the  cool  waters  off  Newfoundland,  Alaska, 
Norway,  and  Japan.     Most  of  the  numerous  small  islands  in  the  Pacific, 


Fig.  148.  —  Coral  reef,  Australia. 

and  some  in  other  tropical  waters,  have  been  built  by  coral  animals,  which 
flourish  in  such  numbers  that  their  skeletons,  converted  into  limestone 
rock,  are  piled  up  by  the  waves  into  low  ring-shaped  reefs  and  islands. 

Economic  Relations.  —  The  sea  never  affords  a  home  or  fixed 
habitation  for  man.  It  is  essentially  a  wide,  empty  space  which 
he  cannot  occupy  or  permanently  control,  but  which  he  can 
cross  whenever  he  chooses.  It  therefore  plays  two  contrasted 
parts  in  human  affairs.  It  is  at  the  same  time  a  barrier  which 
separates  one  people  from  another,  and  a  broad,  free,  uncrowded 
highway  of  communication  between  them.  It  keeps  nations 
apart  and  forms  the  most  easily  defended  boundary  of  states, 


I5B 


PHYSICAL  GEOGRAPHY 


and  it  brings  all  the  nations  of  the  world  together,  enabling' them 
to  exchange  goods  and  ideas.  It  is  generally  barren  and  unpro- 
ductive in  itself,  but  the  people  who  use  it  most  become  rich, 
powerful,  and  enlightened. 

With  the  introduction  of  steam  vessels  in  the  early  part  of  the  nineteenth 
century,  the  transformation  of  the  sea  from  a  barrier  of  separation  to  a 
highway  of  communication  was  begun.  The  change  may  now  be  said  to  be 
complete,  and  constitutes  the  most  important  adaptation  yet  made  by  man 
to  his  environment.  More  than  by  any  other  means,  the  mobility  and  cir- 
culation of  men  and  goods  has  been  promoted  by  the  use  of  the  sea.  Since 
man  is  essentially  a  land  animal,  adaptation  to  the  sea  is  for  him  more 
difficult  than  to  the  land.  Consequently  the  use  of  the  sea  has  required  and 
developed  the  highest  types  of  intellect.  It  requires  more  skill  and  courage 
to  command  an  ocean  vessel  than  to  run  a  railroad  train.  A  modern  first- 
class  passenger  and  freight  steamship  or  a  battleship  is  the  most  com- 
plex and  costly  piece  of  mechanism  on  a  large  scale  man  has  yet  achieved. 
To  construct  and  run  it  requires  all  the  material  and  mental  resources  of 
engineering.  The  profits  and  rewards  of  ocean  traffic  are  so  large  that  the 
great  nations  of  the  world  rival  one  another  in  the  invention  and  construc- 
tion of  merchant  vessels  to  carry  their  goods,  and  of  warships  to  protect 
them. 

The  sea  promotes  civilization  also  by  bringing  people  into 
many-sided  relationships.  Along  its  land  boundaries  a  nation 
is  in  contact  with  one  or  a  few  foreign  neighbors,  but  if  it 
has  even  one  seaport  it  is  brought  in  contact  with  people  from 


Fig.  149.  —Map  of  Pi 


Canal  and  the  Canal  Zone. 


THE   SEA  159 

nearly  every  part  of  the  world.  Sea  trade  is  being  greatly  modi- 
fied and  facilitated  by  cutting  through  the  narrow  isthmuses 
at  Suez  and  Panama.  To  go  around  the  world  by  sea,  it  will 
soon  be  no  longer  necessary  to  sail  around  the  Cape  of  Good 
Hope  and  Cape  Horn,  but  by  the  short-cut  canals  the  whole 
voyage  may  be  made  between  35°  N.  Lat.  and  the  equator. 

The  great  maritime  nations  have  cooperated  in  making  a  careful  survey 
of  all  the  coasts  of  the  world,  and  have  published  charts  showing  the  depth 
of  water,  the  trend  of  coast  lines,  and  the  position  of  islands  and  light- 
houses, and  giving  sailing  directions  for  the  use  of  mariners.  The  great 
commercial  peoples  live  around  the  north  Atlantic,  which  thus  becomes  the 
oceanic  center  of  the  world.  The  north  Pacific  bids  fair  to  become  in  the 
near  future  a  secondary  center  of  scarcely  less  importance. 


Classification  of  Coasts  (Fig.  150). 

(i)  Folded  mountain  coasts,  elevated.  —  Slopes  steep  above  and  below 
water.  Coastal  plains  and  shelves  absent  or  narrow.  Large  rivers,  deltas, 
and  estuaries  rare.  Fiords  in  high  latitudes.  Sea  cliffs  almost  continuous. 
Few  harbors  available  for  seaports. 

(2)  Folded  mountain  coasts,  depressed.  —  Coast  line  double.  Outer  line 
of  partly  submerged  mountain  chains,  forming  festoons  of  islands.  Slopes 
very  steep.  Inner  Hne  of  deep  border  seas  with  numerous  gulfs,  bays,  and 
peninsulas.     Very  complex.     Harbors  numerous. 

(3)  Fault  scarp  coasts.  —  High,  smooth,  and  unindented.  Coastal  plains 
and  shelves  absent  or  narrow.  Estuaries  and  drowned  valleys  absent. 
Deltas  at  the  mouths  of  large  rivers  only.  Fiords  in  high  latitudes. 
Harbors  rare. 

(4)  Plain  coasts.  —  Bordered  by  wide  coastal  plains  and  shelves.  Slopes 
gentle.  Barrier  beaches,  lagoons,  and  dunes  extensive.  Estuaries  and 
drowned  valleys  numerous. 


i6o 


CHAPTER  XII 
COASTS  AND   PORTS 

Independently  of  the  work  of  standing  water,  the  large 
features  and  general  character  of  coast  lines  depend  primarily 
upon  the  present  and  past  reUef  of  the  land.  If  in  the  past 
the  land  has  stood  higher  than  at  present  and  the  streams  have 
graded  their  valleys  down  to  base  level,  then  sinking  of  the  land 
drowns  all  the  bars,  lets  tide  water  far  up  the  valleys,  and  con- 
verts them  into  long,  deep  arms  of  the  sea.  Many  of  the  best 
harbors  in  the  world  are  such  drowned  valleys,  or  estuaries  (Figs. 
153,  154,  155).  A  coast  line  which  is  rising,  or  has  been  recently 
elevated,  is  established  upon  what  was  formerly  sea  bottom,  and 
is  therefore  smooth  and  only  slightly  indented  by  stream  valleys. 
It  is  apt  to  be  bordered  by  cliffs  and  to  present  few  inlets  to 
the  land.  The  gulfs  and  bays  are  generally  curved  in  outline 
and  wide  open  to  the  sea  (Fig.  43). 

The  Southern  Continents.  —  Of  all  the  continents  Africa  has 
the  simplest  and  smoothest  coast  line  (Figs.  16,  150).  More  than 
half  of  it  is  bordered  by  plateaus  and  mountains,  and  between 
Guinea  and  Good  Hope  and  on  the  Red  Sea  it  is  bounded  by  a 
fault  scarp.  Much  of  the  Sahara  coast  is  low,  but  there  are  no 
rivers  or  inlets  except  the  mouth  of  the  Nile.  The  coast  of  Aus- 
tralia resembles  that  of  Africa.  But  one  large  river  enters  the 
sea.  The  south  coast  is  smooth  and  cliffed,  with  but  one  large 
break,  —  Spencer  Gulf, — which  is  a  rift  valley  (p.  64).  The  east 
coast  is  bordered  on  the  land  side  by  mountains  and  on  the  sea 
side  by  the  Great  Barrier  coral  reef.  On  the  Atlantic  side  of  South 
America  a  coastal  plain  extends  from  the  northern  end  of  the 
Andes  Mountains  to  Cape  St.  Roque,  and  from  the  mouth  of  the 
Plata  to  the  Strait  of  Magellan,  including  the  deltas  of  the  three 

162 


COASTS  AND   PORTS 


163 


great  rivers  of  the  continent.  Between  Cape  St.  Roque  and  the 
Plata  low  plateaus  and  mountains  rise  from  a  shore  which  is 
Kttle  indented. 

The  Pacific  Coast  of  America.  —  The  Pacific  coast  of  America 
extends  about  12,000  miles  along  the  foot  of  a  lofty  mountain 
system.  The  slopes  above  and  below  sea  level  are  steep,  and 
the  streams  are  generally  insignificant.  Only  the  Colorado  and 
the  Columbia  cut  through  the  mountain  barrier 
(cx'i  ^  and  bring  large  volumes  of  water  from  the  in- 
N^  \  terior.  One  flows  into  the  Gulf  of  Califor- 
nia, the  only  long  sea  arm  on  the  coast 
and  probably  a  rift  valley.  The  other 
has  a  wide  estuary.  South  of  40°  S. 
Lat.  and  north  of  50°  N.  Lat.  this 
coast  is  cut  into  a  ragged  fringe 
of  long,  narrow,  steep-walled  in- 


Fig.  151.  —  Canal  coast,  Alaska. 


lets  and  high  peninsulas,  bor- 
dered by  outlying  islands. 
These  arms  of  the  sea 
are  of  great  depth  and 
often  extend  as  far 
below  sea  level  as 
their  walls  rise  above 
it.  They  are  called 
canals  and  fiords. 
These  coasts  are 
swept  by  west  winds  from  the  ocean,  which  bring  a  heavy  rain- 
fall. On  account  of  large  volume  and  steep  slope  the  streams 
have  great  erosive  power,  and  are  able  to  cut  valleys  far  back 
into  the  mountains.  On  account  of  high  latitude  and  altitude 
the  snowfall  is  heavy  enough  to  fill  the  valleys  with  ice  and  to 
bring  about  glaciation,  which  has  been  more  extensive  in  the 
past  than  it  is  at  present.  The  ice  has  widened  and  deepened 
the  valleys,  converting  them  into  fiords  (Figs.  106,  152,  153, 
154).    The  great  depth  of  water,  amounting  in  some  cases  to 


164 


PHYSICAL  GEOGRAPHY 


4,000  feet,  is  partly  due  to  sinking  of  the  land.  Glaciation  has 
been  more  severe  on  some  coasts  than  on  others,  but  all  fiord 
coasts  owe  their  distinctive  characters  to  ice  action.  Fiord  coasts 
occur  also  in  Norway,  Iceland,  Scotland,  New  Zealand,  Green- 
land, and  Spitzbergen. 

.  Even  after  the  ice  has  disappeared  fiord  coasts  are  generally  unfavorable 
for  human  occupation.  Deep  harbors  are  superabundant,  but  the  shores  arc 
so  high  and  precipitous  that  landing  is  difficult,  and  there  is  little  room  for 


Fig.  152.  — Fiord,  Norway.    Glacier  ia  the  distance. 


settlement.  Land  resources  are  small  and  population  sparse.  The  people 
are  compelled  to  take  to  the  sea  for  a  living  and  become  fishermen  and 
sailors.  In  the  past,  when  the  sea  was  not  so  well  policed  as  at  present, 
the  Norwegian  fiords  were  the  nesting  places  of  pirates,  who  raided  and 
plundered  their  richer  neighbors.  The  scenery  of  the  Norwegian  fiords 
has  long  been  famous  as  among  the  grandest,  but  is  inferior  to  that  of 
Alaska,  where  the  combination  of  sea,  mountain,  forest,  and  glacier  is  un- 
rivaled in  the  world.  Fiord  coasts  of  a  mild  type,  such  as  those  of  Scotland 
and  Maine,  attract  thousands  of  visitors  by  their  agreeable  summer  cHmate 
and  picturesque  scenery. 

Asia.  —  The  Pacific  coast  of  Asia  is  characterized  by  a  series 
of  island  chains  arranged  in  festoons  which  inclose  deep  border 


COASTS   AND   PORTS 


165 


CASCO  BAY 

MAINE 

SCALE  OF  MILES 
0       12      3       4      5       6 


■r-.v."   / 


ll         J 


-\ 


atF'   / 


/^   ,  great/-  "J  /    y2/^ 

Po.^Pad 


HALFWAY  ROCK 


Fig.  153.  —  Part  of  the  Maine  coast.    Fiords  and  islands. 

seas  between  them  and  the  mainland.  The  islands  are  moun- 
tainous and  volcanic,  and  their  slopes  plunge  seaward  into  very 
deep  water  (Fig.  16).  It  looks  as  if  the  earth  crust  of  Asia 
had  sKd  toward  the  sea  and  wrinkled  up  around  the  edge.  The 
mainland  coast  abounds  in  peninsulas,  bays,  and  gulfs  of  varied 
size  and  character,  and  many  large,  navigable  rivers  flow  into 
the  border  seas.  This  coast  in  complexity  and  accessibility  is 
unequaled  elsewhere  in  the  world. 

Between  the  South  China  Sea  and  the  Bay  of  Bengal  the  ends  of  parallel 
mountain  ranges  project  into  the  sea,  but  the  rivers  have  smoothed  the  coast 
line  by  filling  in  the  spaces  between  the  ranges.  The  head  of  the  Bay  of 
Bengal  is  occupied  by  the  enormous  delta  of  the  Ganges-Brahmaputra. 
The  coasts  of  India,  Persia,  and  Arabia  are  defined  by  lines  of  fracture, 
and  are  generally  high  and  without  indentations.    The  lowlands  about  the 


l66  PHYSICAL  GEOGRAPHY 

mouth  of  the  Indus  and  the  nearly  inclosed  Persian  Gulf  lead  to  valleys 
which  are  desert  except  for  irrigation. 

North  Atlantic  Coasts.  —  The  north  Atlantic  exceeds  all  other 
oceans  in  the  number,  variety,  and  area  of  its  coast  waters. 
The  basins  of  the  Caribbean  Sea  and  Gulf  of  Mexico  are  very 
deep  and  bordered  by  submerged  mountain  ranges  forming  a 
festoon  of  islands  similar  to  those  of  Pacific  Asia.  The  Medi- 
terranean Sea  with  its  branches,  on  account  of  its  area,  depth, 
and  complexity,  might  be  considered  a  distinct  ocean  basin. 
It  is  nearly  divided  by  mountain  ranges,  partly  submerged, 
into  four  great  basins  and  several  smaller  ones.  Its  varied 
character  is  partly  due  to  the  faulting  and  sinking  of  great 
blocks  of  the  earth  crust.  Inclosed  by  the  shores  of  three  con- 
tinents, it  has  been  a  center  of  human  activity  and  civilization 
for  five  thousand  years. 

The  North  and  Baltic  seas  are  shallow,  but  penetrate  the  land  almost  as 
far  as  the  Mediterranean.  On  the  American  side  the  Gulf  of  St.  Lawrence, 
leading  to  the  chain  of  Great  Lakes,  occupies  an  analogous  position.  The 
shallow  pan  of  Hudson  Bay  occupies  a  sunken  portion  of  the  interior 
plain  of  North  America  behind  the  highland  of  Labrador,  as  the  White  Sea 
lies  on  the  European  plain  behind  Scandinavia. 

The  American  and  European  coasts  of  the  north  Atlantic  are  low  and 
not  bordered  by  highlands  except  in  the  north.  Many  of  the  river  mouths 
are  drowned,  forming  estuaries.  The  American  and  European  Mediter- 
raneans are  so  nearly  tideless  that  the  rivers  have  been  able  to  build  great 
deltas  such  as  those  of  the  Orinoco,  Mississippi,  Ebro,  Rhone,  Po,  and  Nile. 

Arctic  Coasts.  —  The  coasts  of  the  Arctic  Ocean  are  almost 
everywhere  low  and  bordered  by  a  wide  coastal  plain  and  shelf. 
The  White  Sea  and  the  Gulf  of  Ob  are  the  only  important  arms. 
Large  rivers,  such  as  the  Mackenzie,  Petchora,  Yenisei,  and 
Lena,  have  built  deltas.  On  account  of  the  severe  climate,  and 
the  persistence  of  snow  and  ice  on  land  and  sea,  the  Arctic 
coasts  are  comparatively  inaccessible  and  unfavorable  for  human 
occupation. 

Coast  Factors.  —  The  degree  of  indentation  of  a  coast  may  be  expressed 
mathematically  in  different  ways.     If  the  length  of  the  actual  mainland 


I 


COASTS  AND   PORTS  1 67 

coast  line  of  each  continent  is  divided  by  the  circumference  of  a  circle 
having  an  area  equal  to  that  of  the  continent,  the  following  ratios,  or  coast 
factors,  are  obtained: 

North  America 4.9        Australia 2.0 

Europe 3.5        South  America 2.0 

Asia 3.2         Africa 1.8 

That  is,  North  America  has  a  coast  line  nearly  five  times  as  long  as  the 
shortest  possible,  while  the  coast  line  of  Africa  is  less  than  twice  as  long  as 
necessary. 

If  the  mainland  area  of  each  continent  is  divided  by  the  length  of  its 
coast  line,  the  following  ratios  are  obtained : 

Europe  has  i  mile  of  coast  line  to  151  square  miles  of  area. 


North  America  " 

"            164                ' 

AustraUa            " 

242 

Asia                    " 

368 

South  America  " 

386 

Africa                 " 

593 

That  is,  Europe  has  nearly  four  times  as  much  coast  line  in  proportion  to 
its  area  as  Africa,  and  North  America  has  more  than  twice  as  much  as  South 
America.  These  facts  help  to  explain  why  Africa  is  shut  in,  isolated,  and 
backward,  while  Europe  has  been  the  center  of  the  highest  civilization  for 
3,000  years,  and  why  North  America  has  become  the  chief  center  of  civil- 
ization outside  of  Europe. 

Ports.  —  A  harbor  is  primarily  a  place  of  shelter  from  storms. 
A  port  is  a  gateway  or  place  of  entrance.  In  a  commercial 
sense  a  port  is  a  place  where  vessels  are  loaded  and  unloaded. 
The  existence  of  a  good  port  depends  upon  many  conditions: 

(i)  Accessibility  from  the  water;  that  is,  a  channel  deep  enough 
for  large  vessels,  not  too  crooked,  free  from  rocks  and  shoals,  and 
not  subject  to  fogs. 

(2)  A  harbor  well  protected  from  winds  and  waves,  free  from 
ice  and  strong  currents,  large  enough  to  furnish  anchorage  for 
many  vessels,  and  deep  enough  to  permit  them  to  float  near 
shore. 

(3)  A  long,  low  coast  line ,  where  wharves  may  be  built  to  bring 
vessels  and  vehicles  alongside  of  each  other. 

(4)  Accessibility  from  the  land  by  river,  canal,  or  railroads. 


i68  PHYSICAL  GEOGRAPHY 

River  Ports.  —  The  great  ports  of  the  world  are,  with  few 
exceptions,  situated  at  or  near  the  mouths  of  rivers,  usually  as 
far  inland  as  large  vessels  can  go.  The  distance  of  the  port 
from  the  river  mouth  is  greatly  increased  by  the  drowning  of 
the  lower  valley  and  the  occurrence  of  tides.  These  conditions 
may  convert  a  coastal  plain  with  small,  shallow  rivers,  a  line 
of  barrier  beaches,  and  a  wide  coastal  shelf,  into  a  first-class 
commercial  seaboard.  The  Atlantic  coasts  of  North  America 
and  Europe  furnish  striking  examples  (Fig.  i6). 

Delta  Ports.  —  In  the  delta  of  a  large  river  there  is  usually 
one  distributary  channel  which  is  deep  enough  for  ocean  vessels, 
and  on  this,  at  some  point  where  the  land  is  safe  from  tidal  over- 
flow, a  seaport  is  apt  to  be  located.  New  Orleans,  the  Rhine 
ports,  and  Calcutta  are  examples.  The  growth  of  a  sand  bar 
off  the  mouth  of  the  channel  and  the  shifting  of  the  discharge 
to  some  other  channel  are  difficulties  liable  to  occur. 

New  Orleans,  eighty  miles  from  the  sea,  is  above  the  point  where  the 
Mississippi  divides  into  the  "  passes  '*  of  the  "  goosefoot."  A  sufficient 
depth  of  water  was  maintained  through  the  South  Pass  for  about  thirty 
years  by  Captain  Eads's  jetties,  which  are  embankments  designed  to  nar- 
row the  channel,  quicken  the  current,  and  compel  it  to  remove  the  bar. 
A  jetty  is  now  being  built  at  the  mouth  of  the  Southwest  Pass  (Fig.  69). 

Lagoon  Harbors  lie  behind  beaches,  bars,  spits,  or  reefs.  They  are  well 
protected,  but  are  usually  too  shallow  to  admit  the  largest  vessels  without 
artificial  deepening  (Fig.  28).  Galveston,  Tex.,  Venice  in  the  Adriatic,  and 
Danzig  on  the  Baltic,  are  sitiiated  on  or  behind  barrier  beaches. 

Fiord  Harbors.  —  Fiords  afford  excellent  harbors  as  far  as 
depth  of  water,  clear  entrance,  and  complete  protection  are 
concerned,  but  are  seldom  favorable  for  ports  on  account  of 
high,  steep  shores  and  inaccessibility  from  the  land.  It  is  only 
where  these  features  exist  in  moderate  degree  that  considerable 
seaports  occur,  as  Christiania,  Norway,  and  Glasgow,  Scotland. 
In  the  latter  case  the  fiord  cuts  entirely  through  the  marginal 
highland  and  penetrates  the  lowland,  where  the  little  river 
Clyde  has  been  enlarged  to  a  canal  which  admits  vessels  of  all 
gizes, 


COASTS  AND   PORTS  169 

Where  the  sinking  of  the  land  has  drowned  a  series  of  valleys  parallel 
with  the  coast,  a  chain  of  islands  is  separated  from  the  mainland  by 
straits,  sounds,  and  canals  (p.  163),  which  form  an  "  inside  passage,"  protected 
from  the  open  sea  and  traversable  by  large  vessels.  The  northwest  coast 
of  North  America  and  the  east  shore  of  the  Adriatic  furnish  striking  ex- 
amples (Fig.  151). 

Round  Inlets.  —  A  coast  inlet  with  a  rounded  or  semicircular  outhne  is 
called  a  cuvette,  meaning  a  bowl  or  basin.  Cuvettes  are  sometimes  due  to 
faulting  along  a  succession  of  curves,  as  on  the  west  coast  of  Italy  and 
south  coast  of  France.  The  greatest  seaports  of  the  Mediterranean  — 
Marseilles,  Genoa,  and  Naples  —  are  situated  upon  such  bays. 

Deep  Straits  connecting  large  bodies  of  water  are  highways  of  com- 
merce, and  are  apt  to  develop  important  seaports,  of  which  Constanti- 
nople and  Singapore  are  examples. 

Artificial  Harbors.  —  All  harbors  have  to  be  improved  more  or 
less  by  artificial  works  to  accommodate  large  shipping.  Wharves 
must  be  built,  alongside  of  which  vessels  may  be  tied,  and  facili- 
ties for  transferring  cargoes  must  be  furnished.  Often  channels 
must  be  deepened  by  dredging,  and  in  some  cases  canals  are  dug 
to  admit  ocean  vessels  to  inland  cities. 

Ships  reach  Amsterdam  only  by  the  North  Sea  Canal,  recently  con- 
structed. A  canal  35  miles  long  has  converted  Manchester  from  an  in- 
land manufacturing  city  to  a  seaport  and  financial  center.  At  Hamburg 
$44,000,000  has  been  spent  in  providing  wharves  and  basins,  and  London 
is  facing  the  necessity  of  spending  $100,000,000  to  improve  the  port  and  hold 
supremacy  in  trade.  Large  sums  have  recently  been  spent  in  making  artificial 
harbors  at  Puerto  Mexico,  and  Salina  Cruz,  the  termini  of  the  railroad  across 
the  Isthmus  of  Tehuantepec,  in  Mexico,  and  at  Colon  and  Panama  where 
the  Panama  Canal  reaches  the  sea. 

In  cases  where  it  is  impossible  to  extend  the  sea  into  the  land,  the  land 
is  built  out  into  the  sea  in  the  form  of  a  breakwater,  which  creates  an  arti- 
ficial lagoon  harbor  behind  it.  At  San  Pedro,  California,  the  breakwater  is 
nearly  two  miles  long. 

Lake  Ports  are  generally  situated  on  river  harbors  and  are 
improved  by  dredging  the  river  mouth  and  building  a  break- 
water outside.  The  harbors  of  Chicago,  Cleveland,  and  Buffalo 
are  of  this  character. 


170 


PHYSICAL  GEOGRAPHY 


Fig.  154.  — Drowned  valley  of  the  Hudson:  a  fiord. 

The  Port  of  New  York.  —  New  York  is  situated  upon  a  harbor 
of  a  mild  fiord  type,  combined  with  a  lagoon.  The  lower  Hudson 
is  a  fiord  which  has  been  partly  filled  with  sediment.  The  East 
River  and  Long  Island  Sound  constitute  an  "  inside  passage  " 
between  the  mainland  and  Long  Island.  The  fiord  and  passage 
expand  at  their  junction  into  the  deep  upper  bay.  The  tidal 
currents  are  strong  enough  to  scour  out  the  channels.  The 
shores  furnish  fifty  miles  of  wharf  line  with  deep  water,  and  there 
is  room  enough  to  build  piers  at  right  angles  to  the  shore,  so  as 
to  accommodate  a  large  number  of  ships.  The  lower  bay  is  an 
antechamber  of  an  entirely  different  character.  It  is  a  shallow 
indentation  partly  fenced  from  the  open  sea  by  the  barrier  beach 
of  Coney  Island  and  the  spit  of  Sandy  Hook,  both  of  which 
are  growing  farther  into  the  bay  and  threatening  to  close  it. 
Much  difficulty  and  expense  are  incurred  in  maintaining  a 
channel  deep  enough  for  the  largest  vessels. 


I 


CHAPTER  XIII 


THE  ATMOSPHERE 


Composition.  —  The  atmosphere,  or  gaseous  portion  of  the 
earth,  forms  a  complete  spheroidal  shell  which  surrounds  the 
solid  and  liquid  globe,  and  not  only  rests  upon  the  surface  of 
land  and  sea,  but  also  penetrates  them  to  a  great  depth.  Its 
thickness,  which  is  not  definitely  known,  is  certainly  several 
himdred  miles  and  may  be  many  thousand.  Its  bulk  is  almost 
entirely  made  up  of  five  gases,  which  are  present  in  the  pro- 
portions given  in  the  following  table: 

Composition  of  the  Air 


Gas 


Nitrogen 

Oxygen 

Water  vapor  (average) .  .  . 

Argon 

Carbon  dioxide  (average) 

Air 


99-99 


Per  cent  of  Volume 

Density 

76.95 

.971 

20.61 

i.ios 

I  .40 

.624 

I  .00 

1.380 

0.03 

1529 

These  gases  are  not  united  or  combined  in  any  way,  but  are 
almost  entirely  independent  of  one  another.  They  act  like  five 
separate  and  distinct  atmospheres  occupying  the  same  space  at 
the  same  time.  The  space  which  each  gas  occupies  is  deter- 
mined by  the  balance  between  its  own  expansive  force,  tending 
to  make  it  expand  indefinitely,  and  gravitation,  which  holds  it 
down  to  the  earth.  Carbon  dioxide,  being  the  heaviest  of  all 
these  gases,  does  not  extend  so  far  upward  as  the  others.  Oxygen 
is  a  little  heavier  than  nitrogen,  and  its  relative  proportion 
decreases  in  the  upper  air.    Water  vapor  is  the  Ughtest  of  all, 

172 


THE  ATMOSPHERE  173 

but  its  existence  as  vapor  is  so  far  dependent  upon  a  warm  tem- 
perature that  it  is  absent  at  great  heights. 

HEIGHT  PRESSURE 

MILES  INCHES 

n.it r 1 1 1 \ \ r~ -T-7 1 rl.6 

9.;:! 


1         1 

"            t 

UEGIOX  n 

F  (.-OXSTAXT  T 

1         -67  jF. 

1 

_t 

:.\Tr]iE"i/_ 

i 

i 

RE 

NiTRbcEN 

n  >x  OF  coN\': 

t            i 

1 
'^1 

L 

OXYGEN 

---ARGON  j 

jVAe^J 

CARBON   ^1 
DIOXIDE      j 

3.11 \ --H ---^ •  ^T^] \....^..     16. 

30. 
0  10  20  30  40  50  60  TO  80  90  100  ' 

VOLUME  PER  CENT 
Fig.  156.  —  Composition  of  lower  atmosphere. 

Properties  and  Functions.  —  Oxygen  combines  freely  with  nearly  all  the 
elements,  and  in  its  numerous  compounds  forms  about  half  of  the  whole 
weight  of  the  globe.  By  the  process  of  respiration  it  supports  the  life  of 
all  plants  and  animals,  and  it  is  the  universal  agent  of  combustion.  By 
respiration,  combustion,  decay,  and  other  processes  of  oxidation  the  quan- 
tity of  oxygen  in  the  air  is  being  continually  diminished.  This  loss  is 
partly  compensated  by  the  oxygen  set  free  from  plants  in  the  process  of 
food  manufacture. 

Nitrogen  is  extremely  inert  and  enters  into  combination  with  other 
elements  with  difficulty.  To  it  is  due  nearly  three  fourths  of  the  pressure 
and  density  of  the  air.  Without  it  birds  could  not  fly,  clouds  and  smoke 
would  settle  to  the  ground,  and  the  force  of  the  wind  and  the  loudness  of 
sound  would  be  proportionately  diminished. 

Argon  resembles  nitrogen,  with  which  it  was  confounded  until  near  the 
end  of  the  nineteenth  century. 

Carbon  dioxide  (CO 2),  or  carbonic  acid  gas,  is  a  compound  of  carbon 
and  oxygen  formed  in  the  active,  growing  parts  of  plants  and  in  the  tissues 
of  all  animals  and  given  off  by  them  in  the  process  of  respiration.  It  is 
also  produced  by  the  combustion  of  all  the  ordinary  forms  of  fuel,  and 
sometimes  escapes  in  large  quantities  from  active  volcanoes,  old  volcanic 
regions,  and  from  many  mineral  springs.  It  forms  the  chief  food  supply 
of  plants.  The  green  parts  of  plants  in  the  sunlight  absorb  carbon  dioxide, 
separate  it  into  its  elements,  retain  the  carbon,  and  give  off  the  oxygen. 
Carbon  dioxide  plays  an  active  part  in  rock  formation,  entering  into  combi- 
nation with  lime  and  other  bases  to  form  limestones.  It  also  enters  largely 
into  the  composition  of  the  bones  and  shells  of  animals.  While  the  abso- 
lute quantity  of  carbon  dioxide  is  the  least  of  all  the  principal  constituents 
of  the  air,  the  part  it  plays  in  the  economy  of  nature  is  second  to  none. 


174  PHYSICAL  GEOGRAPHY 

Water  vapor  is  supplied  by  evaporation  from  all  damp  surfaces,  but 
chiefly  from  the  sea.  When  cooled  it  condenses  again  into  water  and  forms 
clouds,  rain,  and  snow.  The  quantity  present  in  the  air  at  diflferent  times 
and  places  is  very  variable,  amounting  sometimes  to  five  per  cent. 

Dust.  —  The  lower  air  generally  contains  more  or  less  matter  in  the 
form  of  dust,  analogous  to  the  sediment  suspended  in  running  water. 
Dust  consists  of  finely  pulverized  rock  hfted  by  the  wind  or  blown  to  great 
heights  by  volcanic  eruptions,  carbon  particles  from  the  smoke  of  fires, 
particles  of  plant  and  animal  tissue,  vegetable  spores,  bacteria,  and  other 
minute  organisms.  A  cubic  inch  of  air  in  dry  regions  may  contain  thousands 
of  these  particles. 

Dust  in  the  air  diffuses  and  scatters  the  rays  of  sunlight.  In  a  dustless 
atmosphere  all  shadows  would  be  a  deep  black,  and  the  sky  itself  would 
appear  black.  Dust  scatters  the  blue  rays  more  than  the  red,  and  is  the 
chief  cause  of  the  blue  color  of  the  sky  and  of  the  red  and  yellow  colors  at 
sunrise  and  sunset.  Dust  plays  an  important  part  in  the  formation  of  fog 
and  clouds  by  supplying  nuclei  upon  which  the  water  vapor  begins  to  con- 
dense. The  dense  fogs  of  London  and  other  cities  occur  when  the  air  is 
full  of  smoke  particles.  Minute  organisms  in  the  air  furnish  the  germs  of 
disease  and  the  agents  of  decomposition,  as  when  fermentation  is  set  up  in 
cider  or  grape  juice  exposed  in  open  vessels. 

Temperature.  —  The  temperature  of  the  air  is  determined  by 
the  amount  of  heat  received  and  absorbed  from  the  sun  and 
earth.  As  the  sun  heat  passes  through  the  air  on  its  way  to  the 
earth,  about  one  third  of  it  is  absorbed  by  the  air  and  goes  to 
raise  its  temperature,  while  the  remaining  two  thirds  reaches 
the  surface  of  the  land  and  water.  A  part  of  this  is  reflected 
back  without  warming  the  earth,  and  another  part,  being  ab- 
sorbed, goes  to  raise  or  maintain  the  temperature  of  the  land 
and  water.  The  warm  earth  in  turn  warms  the  air  next  to 
it  sKghtly  by  conduction  and  still  more  by  radiating  its  heat 
upward. 

The  lower  air  absorbs  much  more  heat  than  the  upper  air, 
and  consequently  is  maintained  at  a  higher  temperature.  This 
is  due  largely  to  the  presence  of  cloud,  fog,  dust,  and  smoke. 
The  larger  proportions  of  carbon  dioxide  and  water  vapor  in 
the  lower  air  also  increase  its  absorptive  power  for  heat.     Cur- 


THE  ATMOSPHERE 


175 


nts  of  warm  air  are  constantly  rising  from  land  and  water  and 
)oling  by  expansion.  In  consequence  of  these  conditions,  the 
mperature  of  the  atmos- 
fiere  falls  at  the  rate  of 
)out  one  degree  for  every 

00  feet  of  ascent,  from  sea 
vel  up  to  a  height  of  six 
r  seven  miles  (Fig.  156). 

Distribution  of  Light  and 
leat.  —  If  the  earth  were  a 
at  disk  and  one  side  were 
Iways  turned  toward  the 
un,  the  sun's  rays  would 
trike  everywhere  at  the 
ame  angle  and  every  part 
)f  that  side  would  be  con- 
stantly and  equally  lighted 
ind  heated  (Fig.  157,^).     If 

1  spheroidal  earth  stood 
^till,  the  same  half  of  it 
would  be  always  lighted 
and  warmed,  but  not  uni- 
formly. The  spot  where  the 
direct  rays  strike  would  be 
strongly  lighted  and  would 
become  very  hot,  but  the 
more  slanting  rays  would 
cause  the  light  and  heat  to 
decrease  in  every  direction 
to  the  margin  of  the  hemi- 
sphere. The  dark  side  of 
the  earth  would  be  uni- 
formly cold.  Thus  the  light 
and  heat  belts  would  be  arranged  concentrically  around  the  cen- 
ter of  the  hghted  side  (Fig.  157,  5).     If  such  an  earth  should 


D 


E 


Fig.  157.  — Distribution  of  light  and  heat  on  the 
earth  under  various  conditions. 


A 


-     8 


176 


THE   ATMOSPHERE  177 

begin  to  rotate  with  the  sun  directly  over  the  equator,  the 
hght  and  heat  belts  would  be  strung  out  into  zones  extending 
around  it  parallel  with  the  equator,  the  Hght  and  heat  would 
decrease  everywhere  uniformly  from  the  equator  to  the  poles, 
and  all  places  would  have  days  and  nights  of  equal  length.  Our 
earth  is  in  about  that  condition  in  March  and  September  (Fig. 
157,  C).  If  a  spheroidal,  rotating  earth  should  begin  to  revolve 
around  the  sun  with  its  axis  inclined  so  that  the  sun  is  not 
always  over  the  equator,  the  light  and  heat  belts  would  follow 
the  sun,  swinging  back  and  forth,  north  and  south,  once  in 
every  revolution.  The  days  and  nights  would  not  be  of  the 
same  length  at  different  places  or  at  the  same  place  at  different 
times.  Thus  a  change  of  seasons  would  occur  such  as  we  have 
upon  our  earth  (Fig.  iS7,  D  and  E). 

Heat  Belts.  —  A  state  of  things  exactly  as  described  above 
exists  on  our  earth  so  far  as  the  light  bdts  are  concerned,  which 
always  extend  around  the  earth  parallel  with  the  equator;  but 
the  heat  belts  are  bent  out  of  shape  by  land  and  water,  by 
winds,  and  by  ocean  currents.  The  land  is  heated  and  cooled 
more  rapidly  than  water,  consequently  continents  are  warmer 
in  summer  and  colder  in  winter  than  oceans  which  receive  the 
same  amount  of  heat  from  the  sun.  In  summer  the  heat  belts 
are  bent  away  from  the  equator  over  the  land  and  toward  the 
equator  over  the  water;  in  winter,  the  reverse.  Heat  belts 
cannot  be  bounded  by  parallels  of  latitude,  like  the  tropics  and 
polar  circles,  but  by  isotherms,  or  lines  of  equal  temperature 
(Figs.  158,  159,  160),  which  are  quite  crooked. 

Winds  and  ocean  currents  carry  their  temperatures,  whether  warm  or 
cold,  to  the  regions  toward  which  they  move,  and  sweep  the  isotherms  along 
with  them.  In  general,  currents  of  air  or  water  moving  from  the  equator 
carry  warmth  with  them  and  bend  the  isotherms  poleward,  and  currents 
moving  toward  the  equator  carry  coolness  and  bend  the  isotherms  equator- 
ward. 

The  isotherms  as  a  whole  shift  north  and  south  with  the  seasons 
according  to  the  varying  angle  of  the  sun's  rays.  They  are  not 
in  exactly  the  same  positions  on  any  two  successive  days.    Their 


78 


l8o  PHYSICAL  GEOGRAPHY 

positions  in  July  and  January,  the  months  of  extreme  position, 
show  the  character  and  extent  of  the  shifting  (Figs.  159,  160). 
Instead  of  calculating  the  temperature  by  months,  it  may  be 
calculated  for  a  series  of  years,  and  the  resulting  isotherms  show 
the  mean  annual  temperatures  (Fig.  158). 

Range  of  Temperature.  —  The  mean  annual  temperature  of 
any  place  is  important,  but  the  temperature  of  the  warmest 
month  and  day,  and  that  of  the  coldest  month  and  day,  are 
more  important.  The  difference  between  the  temperature  of 
the  warmest  month  and  that  of  the  coldest  month  at  any  place 
is  called  the  annual  range.  The  difference  between'  the  temper- 
ature of  the  warmest  day  and  that  of  the  coldest  day  is  called 
the  absolute  annual  range.  The  range  of  temperature  is  greater 
on  land  than  on  water  in  the  same  latitude. 

Bodies  of  water  are  warmed  more  slowly  than  land  in  the  day  and  the 
summer,  and  cooled  more  slowly  at  night  and  in  the  winter.  The  relatively 
uniform  temperature  of  the  ocean  throughout  the  year  and  the  extreme 
variations  of  temperature  on  land  cause  a  marked  contrast  between  oceanic 
and  continental  climates.  The  range  of  temperature  increases  with  latitude, 
because  in  the  course  of  a  year  both  the  angle  of  the  sun's  rays  and  the 
length  of  day  and  night  vary  more  toward  the  poles  than  near  the  equator. 
The  range  of  temperature  is  greater  in  the  northern  hemisphere  than  in 
the  southern  on  account  of  the  large  land  areas  in  one  and  the  expanse  of 
water  in  the  other  (Fig.  161). 

The  mean  annual  temperatures  at  London,  New  York,  Seattle,  and 
Yokohama  are  about  the  same,  but  the  annual  range  at  London  and  Seattle 
is  about  20  degrees,  and  at  New  York  and  Yokohama  about  40  degrees. 
This  is  due  to  the  prevailing  westerly  winds,  which  blow  from  the  ocean  in 
one  case  and  from  the  land  in  the  other. 

Zones  of  Temperature.  —  Along  any  meridian  the  tempera- 
ture changes  gradually,  but  it  is  convenient  to  divide  the  face 
of  the  earth  into  zones  bounded  by  certain  definite  isotherms. 
In  middle  and  high  latitudes  the  summer  temperatures  are  far 
more  important  than  the  winter  temperatures,  because  they 
determine  what  plants  can  grow,  what  crops  can  be  raised,  and 
the  number  of  people  any  region  can  support.  The  annual  iso- 
therm of  70°  in  each  hemisphere  is  not  far  from  the  tropics,  and 


1 


I 


THE  ATMOSPHERE  l8l 

is  practically  the  limit  of  tropical  plants  such  as  palms,  bananas, 
and  dates.  The  isotherm  of  50°  for  the  warmest  month  in  each 
hemisphere  is  about  the  polar  Kmit  of  cereal  grains  and  forest 
trees.  Beyond  that  men  maintain  themselves  only  with  great 
difficulty.  These  lines  surround  two  caps  of  polar  climate,  be- 
tween which  Hes  the  whole  habitable  world.  This  again  is 
divided  into  a  zone  of  tropical  cHmate  and  two  zones  of  tem- 
perate climate,  of  which  the  northern  is  much  wider  than  the 
southern  and  covers  the  most  favorable  regions  for  human  life 
(Fig.  162). 

There  are  many  schemes  for  dividing  the  earth  into  zones  of  tempera- 
ture, among  which  this  is  one  of  the  simplest  and  most  useful.  For  some 
purposes  a  more  exact  and  detailed  subdivision  is  necessary. 

Temperature  Belts.  —  Temperatures  above  70°  may  be  called 
hot,  between  70°  and  50°  temperate,  and  below  50°  cold.  If  the 
isotherms  of  70°  and  50°  for  July  and  January  are  drawn  on 
the  same  map,  the  result  is  a  system  of  nine  zones  which  show 
the  annual  and  seasonal  conditions  of  temperature  with  sufficient 
exactness  (Fig.  164). 

In  the  equatorial  zone,  which  Hes  approximately  between  the  tropics, 
the  average  monthly  temperature  is  above  70°  at  all  seasons.  The  sub- 
tropical zones  are  hot  with  a  temperate  season,  or  temperate  with  a  hot 
season.  In  the  temperate  zones  the  monthly  temperature  would  be 
between  70°  and  50°  at  all  seasons,  if  it  were  not  for  the  influence  of  the 
land  masses.  In  the  northern  hemisphere  these  truly  temperate  condi- 
tions are  reversed  over  nearly  all  the  land  surface  of  the  zone.  In  North 
America  and  Eurasia  wide  areas  have  hot  summers  and  cold  winters,  and 
the  climate  deserves  the  name  of  intemperate.  These  regions  have  a  tem- 
perate climate  in  spring  and  fall,  a  hot  summer  and  a  cold  winter.  In  the 
southern  hemisphere  these  intemperate  conditions  prevail  only  in  small 
portions  of  South  America  and  AustraHa.  The  rest  of  the  zone  is  truly 
temperate.  The  cold  temperate  zones  have  a  temperate  climate  with  a 
cold  season,  or  a  cold  climate  with  a  temperate  season.  In  the  polar  caps 
the  monthly  temperature  is  below  50°  at  aU  seasons. 

Pressure.  —  At  sea  level  a  cubic  foot  of  air  weighs  about  one 
ounce  and  a  quarter,  and  the  weight  of  all  the  air  above  sea 
level  produces  an  average  pressure  of  14.74  pounds  upon  every 


l82 


i84 


PHYSICAL  GEOGRAPHY 


square  inch  of  surface.  This  pressure  is  equal  in  all  directions, 
—  downwards,  upwards,  or  sidewise  at  any  angle.  The  pressure 
of  the  air  is  measured  by  the  barometer. 

Density.  —  The  air  being  easily  compressed,  its  density  is 
proportional  to  the  pressure  to  which  it  is  subjected,  and  con- 
sequently diminishes  as  the  height  above 
the  sea  increases.  Density  and  pressure 
are  also  influenced  by  other  conditions,  of 
which  temperature  and  humidity,  or  quan- 
tity of  water  vapor  it  contains,  are  the 
most  important.  When  air  is  heated  it 
expands  and  becomes  less  dense.  The 
same  effect  is  produced  by  the  addition  of 
water  vapor.  On  warm,  damp  days  the 
pressure  and  density  are  less,  and  the  ba- 
rometer stands  lower  than  on  cold,  dry 
days. 

The  distribution  of  pressure  is  shown  on  a  map 
by  isobars,  or  lines  drawn  through  places  where 
the  pressure  is  the  same  (Figs.  165,  166). 

Laws  of  Winds.  —  Of  all  the  materials 
of  the  earth,  the  air  is  the  most  mobile 
and  sensitive  to  change.  When  air  is 
heated  or  made  more  damp  by  the  addi- 
tion of  water  vapor,  it  expands  and  be- 
comes less  dense  than  the  surrounding  air, 
which  crowds  in  from  all  sides  and  buoys 
the  lighter  air  upward.  The  updraft  in 
a  chimney  or  over  an  open  fire,  and  the  slower  movement  of  the 
air  toward  the  fire,  furnish  famiHar  examples  of  convection  cur- 
rents on  a  small  scale.  Every  wind  that  blows  is  a  part  of  a 
similar  movement,  in  which  gravitation  pulls  heavy  air  down- 
ward and  compels  light  air  to  move  upward.  In  the  regions  of 
ascending  and  descending  air  the  movement  is  usually  impercep- 
tible and  a  calm  prevails,  but  between  these  regions,  which  may 


y!' 


Fig.  163. — Two  forms  of  the 
barometer. 


i86 


i88 


PHYSICAL  GEOGRAPHY 


'""'"" 


HIGH 


AAAH  I 


LOW 


HIGH 


Fig,  167. — Pressure  and  direction  of  wind. 


be  hundreds  or  thousands  of  miles  apart,  horizontal  currents 
exist  which  constitute  the  surface  winds.     Where  the  pressure 

as  measured  by  the 
barometer  is  high  the 
vnH  air  is  heavy  and  set- 
tling; where  the  pres- 
sure is  low  ^the  air 
is  light  and  rising. 
Hence  the  first  law:  Winds  always  blow  from  regions  of  high  pres- 
sure to  regions  of  low  pressure  (Figs.  177-180). 

Gravitation  acting  alone  would  make  air  move  from  a  region 
of  high  pressure  to  a  region  of  low  pressure  by  the  shortest 
path,  crossing  the  isobars  at  right  angles,  just  as  it  makes  water 
flow  down  a  slope  by  the  steepest  course;  but  other  influences 
make  the  course  of  the  wind  less  direct.  Second  law:  The  rota- 
tion of  the  earth  turns  winds  blowing  from  any  direction  to  the 
right  of  a  direct  course  in  the  northern  hemisphere,  and  to  the  left 
in  the  southern. 

The  greater  the  difference  of  pressure  between  two  regions 
the  faster  the  air  moves.  Third  law:  Where  the  isobars  are  close 
together  the  winds  are  steady  and  strong,  and  where  the  isobars  are 
far  apart  the  winds  are  light  and  shifting. 

Distribution  of  Pressure.  —  On  account  of  the  constantly  high 
temperature  near  the  equator  the  pressure  there  is  generally  low 
(Figs.  165,  166),  but  in  middle  latitudes  the  land  is  colder  than 
the  water  in  winter  and  warmer  in  summer,  and  this  produces 
rounded  or  elHptical  areas  of  high  and  low  pressure  which  change 
their  positions  with  the  seasons.  In  the  northern  winter  very 
high  pressures  prevail  over  the  interior  of  Asia  and  North 
America,  and  low  pressures  over  the  north  Atlantic  and  Pacific 
oceans.  In  summer  the  conditions  are  reversed.  In  the  south- 
ern hemisphere  the  land  masses  never  get  cold  enough  to  have 
higher  pressures  than  the  oceans.  In  winter  (Fig.  165)  a  belt 
of  high  pressure  extends  along  the  southern  tropic  nearly  around 
the  earth,  crossing  land  and  sea  except  a  gap  in  the  south  Pacific. 


THE  ATMOSPHERE 


189 


In  summer  (Fig.  166)  the  heated  continents  break  this  belt  into 
three  parts,  one  over  each  ocean.  In  spite  of  the  very  low  tem- 
peratures in  the  polar  regions,  the  pressures  there  are  generally 
low  because  there  is  less  air  above  them. 

Cyclones  and  Anticyclones.  —  The  winds  blow  outward  from 
centers  of  high  pressure  in  all  directions.  The  movement  starts 
along  radial  lines  like  the  spokes  of  a  wheel,  but  the  rotation  of 


NORTHERN 


SOUTHERN 


NORTHERN 


SOUTHERN 


Fig.  168.  —  Cyclone. 


Fig.  169. — Anticyclone. 


the  earth  (second  law)  changes  it  to  a  spiral  movement  clock- 
wise in  the  northern  hemisphere  and  counterclockwise  in  the 
southern  (Fig.  169).  The  winds  blow  inward  toward  centers  of 
low  pressure  from  all  directions,  but  the  rotation  of  the  earth 
gives  them  a  spiral  motion  counterclockwise  in  the  northern  hemi- 
sphere and  clockwise  in  the  southern  (Fig.  168).  As  the  winds 
approach  the  center,  they  are  crowded  into  a  narrower  space, 
their  velocity  increases,  and  their  paths  become  more  nearly 
circular  imtil  a  whirl  or  eddy  is  set  up.  The  movement  is  like 
that  of  water  running  out  through  a  hole  in  the  bottom  of  a 
bowl,  only  the  air  escapes  upward  instead  of  downward.  A 
mass  of  air  moving  spirally  inward  toward  a  center  of  low  pres- 
sure is  called  a  cyclone.  The  path  of  the  wind  in  a  cyclone  in  the 
northern  hemisphere  is  a  curve  like  the  figure  6 ;  in  the  southern 
hemisphere  Hke  a  reversed  6.  A  mass  of  air  moving  spirally 
outward  from  a  center  of  high  pressure  is  called  an  anticyclone. 

Wind  Belts.  —  The  prevaiKng  low  pressures  in  the  equatorial 
regions  and  the  presence  of  areas  of  high  pressure  in  the  tropi- 
cal regions  divide  the  earth  into  wind  belts,  which  are  more 
regular  in  the  southern  hemisphere  than  in  the  northern.  Near 
the  equator  the  air  is  always  Varm  and  rising,  a  condition  which 


I  go  PHYSICAL   GEOGRAPHY 

produces  a  belt  of  equatorial  calms.  Between  the  equatorial 
calms  and  the  southern  tropical  regions  the  general  movement 

is  toward  the  equator  and  westward, 
producing  a  belt  of  constant  southeast 
trade  winds.  South  of  the  southern 
tropical  regions  the  air  moves  steadily 
and  strongly  eastward  in  a  great  spi- 
ral whirl  around  the  polar  region,  pro- 
ducing a  belt  of  almost  constant  west 
winds.  The  movement  of  air  within 
the  Antarctic  circle  is  not  well  known. 
^*  ^^°'  Between  the  equatorial  calms  and 

the  northern  tropical  regions  is  a  belt  of  northeast  trad^  winds, 
but  these  are  not  so  regular  and  constant  as  the  southeast ^  trades. 
North  of  the  northern  tropical  regions  there  is  a  belt  of  prevail- 
ing westerly  winds,  but  on  account  of  the  large  land  masses,  with 
their  changing  temperatures  and  pressures,  these  winds  are  not 
so  regular  and  constant  as  the  west  winds  of  the  southern  hemi- 
sphere. There  is  something  like  a  north  polar  whirl,  but  it  is 
broken  up  by  the  areas  of  low  pressure  over  the  oceans  in  winter 
and  over  the  continents  in  summer.  Along  the  southern  tropic 
and  a  little  north  of  the  northern  tropic  there  are  belts  of  rela- 
tively high  pressure,  where  the  air  is  descending,  and  from  which 
the  trades  and  westerly  winds  blow.  These  are  called  the  tropical 
calms.  The  conditions  in  the  southern  hemisphere  show  what 
the  planetary  system  of  winds  would  be  if  the  land  masses  did 
not  interfere.  This  ideal  system,  to  which  the  actual  system 
approaches  more  or  less  closely,  is  shown  in  Fig.  170,  which 
should  be  carefully  studied  and  used  as  a  key  to  the  actual 
system. 

The  wind  belts,  like  the  temperature  belts,  shift  north  and 
south  with  the  seasons,  following  the  position  of  the  vertical  sun 
in  the  heavens  (Figs.  165,  166,  171,  172). 

Monsoons.  —  The  greatest  disturbing  influence  in  the  wind 
system  is  the  large  land  mass  of  Asia.     In  winter  it  is  an  area 


OCEAN  WINDS.  JULY  AND  AUGUST 


^ 


l^ ' 


r. 


ISO  160 


Le.ss  than  18  Mi/e,s  an  hour ^Ivahable  Winds 

uver  It  M  »j  _.       , 

_ /  St&ac/y       /, 

Fig.  171. 
■OCEAN  WINDS.  JANUARY  AND  FEBRUARY 


100  120 


Les^s_  than  IQ  Mil&s  an  hour  -—^y^riable  Winds 
).  Steady      « 


Fig.  172. 
191 


192  PHYSICAL  GEOGRAPHY 

of  low  temperature  and  very  high  pressure,  from  which  the  winds 
blow  outward  in  all  directions  (Fig.  172).  In  summer  it  is  an 
area  of  high  temperature  and  low  pressure,  which  deflects  the 
belt  of  calms  far  north  of  the  equator  (Fig.  171).  At  this  season 
the  southeast  trades  over  the  Indian  Ocean  cross  the  equator  and, 
turning  eastward,  become  the  southwest  monsoon,  while  over  the 
western  Pacific  the  northeast  trades  become  southerly  and  south- 
easterly winds  (Fig.  171).  These  directions  are  opposite  to  the 
wind  directions  in  winter.  Winds  which  are  thus  reversed  with 
the  seasons  are  called  monsoons.  Less  important  monsoon  re- 
gions exist  upon  the  west  coasts  of  Africa  and  South  America. 

Economic  Relations.  —  Winds  are  of  the  greatest  importance 
to  the  life  of  plants,  animals,  and  men  because  they  transfer 
great  masses  of  air  from  one  part  of  the  earth  to  another.  They 
carry  the  conditions  of  temperature  and  moisture  which  exist 
in  the  regions  from  which  they  come  to  the  regions  over  which 
they  blow,  and  as  they  go  on  they  themselves  gradually  acquire 
new  conditions.  Winds  blowing  over  warm  waters  become 
warm  and  laden  with  water  vapor,  which  they  let  fall  as  rain 
upon  the  land.  Winds  from  a  large  land  mass  are  dry  and  may 
be  the  cause  of  desert  conditions  in  lands  to  which  they  blow. 
Winds  moving  from  a  warmer  to  a  colder  region  bring  warm, 
damp  weather,  and  winds  blowing  from  a  colder  to  a  warmer 
region  bring  cool,  dry  weather.  Winds  blowing  from  the  ocean 
against  a  mountain  range  or  plateau  bring  heavy  rainfall  to  the 
windward  side  and  little  or  no  rain  to  the  leeward  side  (Fig.  185). 
Rising  air  is  always  cooled  and  generally  causes  cloud  to  form 
and  rain  to  fall.  Descending  air  is  warmed,  and  brings  clear, 
dry  weather. 

Most  changes  of  weather  are  due  to  changes  in  the  direction  of  the 
wind.  Some  winds  are  agreeable  and  favorable  to  life;  some  bring  suffer- 
ing, destruction,  and  death.  Even  light  breezes  effect  a  continual  change 
of  air,  which  brings  more  food  to  plants  and  animals  and  removes  waste 
and  injurious  gases. 


CHAPTER  XIV 
MOISTURE   IN   THE   AIR 

Capacity  and  Humidity.  —  The  atmosphere,  as  well  as  the 
ocean,  is  a  great  reservoir  of  water.  Everywhere  over  the  face 
of  the  earth  the  air  contains  a  variable  quantity  of  invisible 
vapor,  which  may  amount  to  as  much  as  five  per  cent.  If  all 
the  vapor  in  the  air  should  be  condensed  and  fall  as  rain,  it 
would  be  sufficient  to  cover  the  whole  face  of  the  earth  with 
water  to  the  depth  of  one  inch.  Water  is  constantly  evapo- 
rating from  the  sea,  lakes,  rivers,  and  land  surface.  Even  ice 
evaporates,  but  the  higher  the  temperature  of  the  water  the 
more  rapid  is  the  evaporation.  The  quantity  of  water  vapor 
which  can  exist  in  any  given  space  increases  with  the  temperature 
of  the  vapor,  whether  the  space  is  already  filled  with  air  or  not. 
Warm  air  can  contain  more  vapor  than  cold  air  because  the  air 
determines  the  temperature  of  the  vapor  in  it.  When  the  space 
or  air  contains  all  the  vapor  it  can  hold,  it  is  said  to  be  saturated. 
The  table  on  page  194  gives  the  weight  of  vapor  which  can  exist 
in  a  cubic  foot  of  space  or  air  at  various  temperatures.  These 
quantities  are  called  the  capacity  for  vapor. 

When  water  evaporates  it  expands  instantly  to  about  1,700  times  its 
liquid  volume,  and  the  vapor  rapidly  diffuses  itself  through  the  air  in 
the  vicinity.  The  evaporation  and  diffusion  are  hastened  by  currents  of 
air  which  carry  the  vapor  away  from  the  evaporating  surface.  The  dry- 
ness or  dampness  of  the  air  is  measured  not  by  its  absolute  humidity,  or 
the  quantity  of  vapor  actually  present  in  it,  but  by  its  relative  humidity,  or 
the  ratio  of  its  absolute  humidity  to  its  capacity.  If  the  air  out  of  doors 
is  at  a  temperature  of  32°,  and  contains  two  grains  of  vapor  in  each  cubic 
foot,  it  is  very  damp,  because  it  is  nearly  saturated;  but  if  the  same  air 
is  brought  into  the  house  and  heated  to  70°,  it  becomes  very  dry,  because 

193 


194 


PHYSICAL   GEOGRAPHY 


GRAINS    OF    WATER    VAPOR    IN    A    CUBIC    FOOT    OF    SATURATED    SPACE    OR    AIR    AT 
VARIOUS  TEMPERATURES 


IO° 

■  11(^ 

34° 

2.279 

58° 

5-370 

82° 

11.626 

12° 

.856 

36° 

2-457 

60° 

5 

745 

84° 

12.356 

14° 

.941 

K 

2.646 

62° 

6 

142 

86° 

13.127 

i6° 

1.032 

4° 

2.849 

64° 

6 

563 

88° 

13  937 

i8° 

1. 128 

K 

3.064 

66° 

7 

009 

90° 

14.790 

20° 

I  235 

K 

3  294 

68° 

7 

480 

92° 

15-689 

22° 

1-355 

46° 

3-539 

70° 

7 

980 

94° 

16.634 

24° 

1.483 

48° 

3.800 

72° 

8 

508 

96° 

17.626 

26° 

1.623 

50° 

4.076 

74° 

9 

066 

98° 

18.671 

28° 

1-773 

52° 

4-372 

76° 

9 

655 

100° 

19.766 

3°: 

1-935 

^^\ 

4.68s 

78° 

10 

277 

102° 

20.917 

32° 

2. 113 

56° 

5.016 

80° 

10 

934 

104° 

22. 125 

it  is  then  only  one  fourth  saturated.  This  is  the  reason  why  air  in  heated 
rooms  in  the  winter  is  generally  too  dry  for  comfort  and  health,  and  pans 
of  water  should  be  placed  where  they  will  supply  more  moisture. 

Unsaturated  air  is  always  ready  to  take  up  more  moisture, 
but  if  saturated  air  at  any  temperature  is  cooled  a  part  of  the 
vapor  immediately  condenses  into  water.  If  a  bright  tin  cup 
is  filled  half  full  of  warm  water,  and  cold  water  or  ice  is  added, 
the  cup  will  generally  get  cold  enough  to  cause  a  deposit  of  dew 
on  the  outside.  The  dew  is  formed  by  condensation  of  vapor 
from  the  air.  This  is  the  reason  why  a  pitcher  or  glass  of  cold 
water  will  sometimes  ''  sweat  "  in  warm  weather. 

If  the  water  in  the  tin  cup  is  stirred  with  a  thermometer,  the  temperature 
observed  at  the  moment  of  the  first  appearance  of  dew  is  called  the  dew 
point.  It  is  the  temperature  of  saturation,  and  from  it  the  absolute  humid- 
ity may  be  found  by  consulting  the  table.  The  capacity  of  the  air  may 
be  found  by  noting  its  temperature  and  again  consulting  the  table.  The 
absolute  humidity  divided  by  the  capacity  gives  the  relative  humidity.  If 
the  temperature  of  the  air  is  70°,  its  capacity  is  7.980  grains  to  the  cubic 
foot.  If  the  dew  point  is  40°,  the  absolute  humidity  of  the  air  is  2.849 
grains,  and  its  relative  humidity  is  2.849  ^  7-98o,  or  35.7  per  cent.  That 
is,  the  air  is  35.7  per  cent  full,  and  is  moderately  dry. 

Condensation.  —  When  air  is  cooled  below  its  dew  point, 
some  of  the  vapor  condenses  into  dew,  frost,  fog,  cloud,  rain,  or 
snow.  The  atmosphere  is  cooled  and  its  vapor  condensed  by 
several  processes. 


I 


MOISTURE   IN   THE  AIR 


195 


1.  Expansion. —  Whenever  air  rises  it  expands,  and,  without  any  trans- 
fer of  heat  to  other  bodies,  it  is  cooled  one  degree  for  every  183  feet  of 
ascent.  As  soon  as  the  temperature  falls  below  dew  point  and  conden- 
sation begins,  cooling  is  retarded  or  stopped.  Descending  air  is  always 
warmed  by  compression  one  degree  for  every  183  feet  of  descent;  hence 
condensation  seldom  occurs  in  descending  air. 

2.  Radiation.  —  If  the  air  stands  or  passes  over  or  near  cooler  objects, 
as  the  ground,  the  sea,  snow,  ice,  or  a  mass  of  cooler  air,  it  radiates  its 
heat,  its  temperature  falls,  and  condensation  may  occur.  This  usually 
takes  place  when  winds  blow  from  warmer  to  cooler  regions. 

3.  Coftduction.  — Air  in  contact  with  a  cooler  body  loses  heat  by  con- 
duction. This  process  is  less  important  than  is  commonly  supposed,  be- 
cause air  is  a  poor  conductor  of  heat  and  only  that  portion  which  actually 
touches  a  cooler  body  is  cooled  in  this  way.  Dew  and  frost  are  generally 
deposited  from  air  in  contact  with  a  cold  surface. 

4.  Mixture.  — When  warm  air  is  mixed  with  cool  air,  the  temperature  of 
the  mixture  may  fall  below  the  dew  point  and  condensation  may  take  place. 


Fig.  173.  — Fog  seen  from  mountain  top  above  it,  California. 


Clouds.  —  When  water  vapor  is  condensed  in  the  air,  it  be- 
comes visible  as  fog  or  cloud,  which  is  composed  of  minute 
particles  of  liquid  water  or  ice,  a  sort  of  water  dust.     Fog  is 


196 


PHYSICAL   GEOGRAPHY 


pa 

liMir 

iH.    ■  -^^1 

*._  "W 

S^JIiJ 

PUPp.^:^  -^^ 

Copyright,  1906,  by  F.  M.  Locke. 

Fig.  174. — Upper  part  of  cumulus  clouds. 


Fig.  175.  —  Stratus  clouds. 


formed  at  or  near  the  surface  of  land  or  water,  cloud  at  higher 
altitudes.  Clouds  usually  settle  slowly  and,  on  reaching  a 
layer  of  warmer  or  drier  air,  evaporate.  If  condensation  con- 
tinues they  are  renewed  above  as  fast  as  they  evaporate  below. 


I 


MOISTURE   IN  THE   AIR 


197 


Cumulus  clouds  are  rounded  masses  which  look  white  in  sunlight  and 
dark  in  shadow.  They  begin  to  form  at  the  level  where  a  rising  column 
of  air  reaches  the  dew  point,  and  may  be  piled  up  to  a  height  of  five  miles 
or  more.  They  are  common  in  equatorial  regions  and  on  calm  summer 
afternoons,  when  the  air  which  starts  upward  in  the  morning  has  reached 
a  sufficient  height.  They  often  bring  showers  and  thunderstorms  and 
hence  are  sometimes  called  "  thunder  heads." 


Fig.  176.  —  Cirrus  clouds. 


Cirrus  clouds  are  light,  feathery  clouds  formed  at  great  heights,  where 
the  vapor  condenses  into  minute  crystals  of  snow  or  ice. 

Stratus  clouds  lie  in  low,  horizontal  bands,  or  continuous  sheets. 

Nimbus  or  storm  clouds  are  stratus  clouds  from  which  rain  or  snow 
falls  when  the  sky  is  overcast. 

There  are  many  forms  and  varieties  of  cloud  intermediate  between 
cumulus,  cirrus,  and  stratus,  of  which  a  dozen  or  more  are  common  and 
have  compound  names,  such  as  strato-cimiulus,  cirro-cumulus,  and  cirro- 
stratus. 

Precipitation.  —  When  clouds  become  sufficiently  dense  the  air 
is  no  longer  able  to  buoy  up  or  evaporate  them,  and  the  water 
falls  as  rain,  or,  if  the  temperature  of  the  cloud  is  below  freezing, 
as  snow  or  hail.  Snowflakes  are  formed  by  the  direct  conden- 
sation of  vapor  into  six-angled  crystals  of  many  symmetrical 


ipS  PHYSICAL  GEOGRAPHY 

forms,  which  are  usually  tangled  together  before  reaching  the 
earth.  Hailstones  are  rounded  masses  of  snow  and  ice  which 
have  passed  through  several  layers  of  alternating  warmer  and 
colder  air. 

Precipitation  is  measured  by  the  rain  gauge.  Any  open  vessel  with 
vertical  sides  wiU  serve  the  purpose.  The  amount  of  rainfall  or  precipi- 
tation is  measured  in  inches  of  depth  of  water  caught,  snow  being  first 
melted.  In  middle  latitudes  one  inch  of  rain  a  day  is  a  large  fall,  but 
sometimes  an  inch  falls  in  an  hour.  In  tropical  regions  a  rainfall  of  40 
inches  has  been  recorded  in  a  single  day.  One  inch  of  rain  amounts  to 
113  tons  of  water  on  one  acre  of  surface. 

Dew  and  Frost.  —  Dew  and  frost  are  produced  by  the  con- 
densation of  vapor  upon  any  cold  surface.  The  deposit  is 
heavier  during  clear,  still  nights  and  upon  surfaces  which  radiate 
heat  freely.  On  still  nights  the  cooler  air  settles  into  valleys 
and  depressions  and  produces  heavier  dew  or  frost  there  than  on 
elevations.  A  slight  cover,  as  a  tree,  or  even  a  piece  of  paper, 
may  prevent  cooling  to  the  dew  or  frost  point. 

The  dates  of  the  last  killing  frost  in  the  spring  and  the  first  in  the  fall 
are  very  important  as  limiting  the  growing  season  for  crops.  In  central 
United  States  the  date  of  the  first  frost  in  the  fall  may  vary  as  much  as 
a  month  in  different  years,  and  its  occurrence  a  month  earlier  than  usual 
may  result  in  miUions  of  dollars'  damage  to  the  corn  crop.  A  temperature 
near  freezing  may  be  destructive  to  fruits  which  are  in  blossom  or  approach- 
ing maturity,  and  even  trees  and  vines  themselves  may  be  killed.  Orchards 
and  fields  are  sometimes  protected  by  a  covering  of  light  cloth,  like  a  tent, 
by  ditches  or  pipes  containing  hot  water,  by  fires,  or  by  filling  the  air  with 
smoke  which  acts  as  a  blanket.  The  presence  of  a  body  of  water,  even  a 
small  pond,  may  be  sufficient  to  prevent  unseasonable  warm  spells  in  the 
spring  and  early  frosts  in  autumn.  For  this  reason  the  shores  of  lakes 
Ontario,  Erie,  and  Michigan  and  the  Finger  Lakes  of  New  York  are 
bordered  by  belts  of  vineyards,  peaches,  and  small  fruits. 

Storms.  —  Outside  the  tropics  a  large  part  of  the  rainfall  is 
brought  by  storms,  or  temporary  disturbances  which  travel 
through  the  atmosphere  along  definite  paths.  They  bring  to 
the  regions  over  which  they  pass  shifting  winds  and  usually 
cloudiness  and  precipitation.     If  no  precipitation  occurs  they 


i 


MOISTURE   IN  THE  AIR  199 

are  called  wind  storms.  The  winds  may  be  gentle  or  extremely 
violent,  as  in  the  hurricane  and  tornado.  In  nearly  all  storms 
the  movement  of  air  is  spirally  inward,  toward  and  around  a 
center  of  low  pressure,  and  they  may  be  described  as  traveling 
cyclones.  They  may  be  of  any  size  from  a  summer  dust  whirl 
a  few  feet  in  diameter,  to  a  storm  which  covers  half  a  continent. 
The  whirls  travel  in  the  direction  of  the  general  air  current,  but, 
like  eddies  in  a  river,  continually  take  in  new  air  in  front  as  they 
leave  other  air  behind. 

Weather  Bureaus  and  Maps.  —  Benjamin  Franklin  was  prob- 
ably the  first  man  to  observe  that,  while  long  rain  storms  were 
brought  to  New  England  by  winds  from  the  east,  they  began 
earlier  at  points  farther  west.  To  account  for  these  facts  he 
conceived  the  idea  of  a  large  whirling  storm  which  passed  across 
the  country  from  west  to  east.  Within  the  last  fifty  years  the 
Weather  Bureaus  of  the  United  States,  Canada,  and  European 
countries  have  learned  that  in  the  northern  belt  of  prevailing 
westerly  winds  there  is  a  continual  procession  of  cyclones  moving 
eastward  around  the  earth.  By  following  their  progress  from 
day  to  day,  a  Weather  Bureau  is  able  to  predict  their  arrival 
and  the  kind  of  weather  they  will  bring. 

In  America  and  Europe  hundreds  of  observing  stations  have  been  es- 
tablished, from  which  telegraphic  reports  are  sent  to  a  central  station  at 
a  given  hour  twice  a  day.  From  these  reports  weather  maps  are  made, 
showing  the  temperature,  pressure,  wind  direction,  state  of  the  sky,  and 
precipitation  at  that  hour  for  the  whole  country.  By  means  of  these  maps 
forecasts  are  made  of  what  the  weather  is  likely  to  be  for  the  next  24  or 
48  hours.  It  is  sometimes  possible  to  forecast  the  weather  for  a  week 
or  ten  days.  The  intervals  between  the  cyclones  are  occupied  by  areas  of 
relatively  high  pressure,  or  anticyclones.  As  the  procession  of  cyclones 
and  anticyclones  passes  across  the  country  it  brings  corresponding  changes 
of  weather,  a  knowledge  of  which  is  of  the  greatest  importance  to  farmers, 
sailors,  boatmen,  shippers,  and  all  people  whose  business  or  pleasure  depends 
in  any  degree  upon  the  weather.  Figs.  177-180  show  typical  examples  of 
cyclones  and  anticyclones,  but  their  study  should  be  continued  by  the 
use  of  the  daily  weather  maps  issued  by  the  nearest  Weather  Bureau 
station. 


MOISTURE   IN   THE   AIR  20I 

Cyclones.  —  The  cyclone  shown  in  Fig.  178  (January  29)  is  a 
mass  of  warm,  damp  air,  and  therefore  of  low  pressure,  which 
covers  a  rounded  area  more  than  i  ,000  miles  in  diameter.  The 
pressure  is  lowest  at  the  center,  near  Chicago,  and  increases  in 
every  direction  toward  the  circumference.  The  whole  mass  is 
moving  in  a  spiral  whirl  inward  and  counterclockwise.  In  the 
southern  quarter  the  winds  are  from  the  southwest  and  south, 
in.  the  eastern  quarter  from  the  southeast  and  east,  in  the 
northern  quarter  from  the  northeast  and  north,  and  in  the 
western  quarter  from  the  northwest  and  west.  The  southerly 
and  easterly  winds  bring  to  the  southeast  side  temperatures  above 
freezing,  while  on  the  northwest  side  northerly  winds  bring  tem- 
peratures mostly  below  freezing.  As  the  air  approaches  the 
center  it  rises  and  escapes  upward.  As  it  rises  and  whirls  it 
expands  and  air  from  all  sides  is  mixed  together.  By  expansion 
and  mixture  the  warm,  damp  air  from  the  Gulf  and  Atlantic  is 
cooled,  and  its  vapor  condenses  into  a  layer  of  cloud  which  covers 
nearly  the  whole  area  of  the  cyclone.  Snow  or  rain  has  been 
general  in  the  cyclonic  area  during  the  past  twenty-four  hours 
and  is  still  falling  over  half  of  it.  The  cyclone  is  moving  east- 
ward and  carrying  with  it  warm,  cloudy,  and  stormy  weather, 
which  clears  up  as  the  storm  passes. 

Anticyclones.  —  The  anticyclone  shown  in  Fig.  180  (January 
31)  is  a  mass  of  cold,  dry  air,  and  therefore  of  high  pressure, 
which  covers  an  area  measuring  about  1,200  miles  east  and  west 
and  a  much  greater  distance  north  and  south.  The  pressure  is 
highest,  30.6  inches,  at  the  center  from  Lake  Superior  to  Texas, 
'and  diminishes  toward  the  circumference.  It  may  be  compared 
to  a  long,  smooth  ridge  upon  which  heavy  rain  is  falling  and  the 
water  draining  off  down  the  slopes.  In  like  manner  the  air 
settles  downward  and  spreads  out  from  the  center. 

Water  would  run  down  the  slopes  of  the  hill  by  the  steepest  and  most 
direct  path,  but  the  rotation  of  the  earth  causes  the  air  to  move  slantingly 
down  the  slope  of  pressure  along  lines  to  the  right-hand  of  the  shortest 
path  to  the  bottom.  The  north-south  elongation  of  the  anticyclone  causes 
the  principal  slopes  to  be  toward  the  east  and  west,  and  accordingly  at 


ZQZ 


204  PHYSICAL  GEOGRAPHY 

most  places  in  the  eastern  half  the  winds  are  from  the  northwest  and  north, 
and  in  the  western  half  from  the  southeast.  The  northerly  winds  bring 
clear,  cold  weather  which  extends  from  Port  Arthur,  where  the  thermom- 
eter stands  at  20°  below  zero,  to  New  Orleans,  where  the  temperature 
is  below  freezing.  On  the  west  side  the  temperature  rises,  and  it  is  as 
warm  in  northern  Montana  as  in  Florida.  The  anticyclone  brings  into 
the  midst  of  the  country  dry,  clear  air,  which  is  cold  on  account  of  free 
radiation,  and  the  temperature  changes  more  rapidly  along  east-west  than 
along  north-south  lines.  It  will  move  eastward  and  carry  its  clear,  cold 
weather  to  the  Atlantic  coast.  The  progress  of  low  temperatures  eastward 
in  front  of  an  advancing  anticyclone  is  called  a  cold  wave. 

Procession  of  Lows  and  Highs.  —  Figs.  177-180  show  a  regular 
procession  of  cyclones  and  anticyclones  moving  eastward  during 
four  days. 

On  January  28  a  cyclone,  or  "  low,"  is  passing  from  New  England  over 
the  Atlantic  Ocean.  A  long  ridge  of  moderately  high  pressure  extends 
from  the  upper  lakes  to  Florida,  with  north  and  northwest  winds  and  gen- 
erally clear  sky.  On  the  west  it  descends  to  a  large  oval  area  of  low  pres- 
sure, with  spirally  inflowing  air,  general  cloudiness,  and  a  patch  of  rain  east 
of  the  center.  The  Pacific  states  are  covered  by  a  feeble  anticyclone,  or 
"  high." 

On  January  29  the  same  elements  appear  with  changed  positions,  areas, 
and  intensities.  The  principal  center  of  low  pressure  has  moved  from 
Kansas  to  Illinois,  and  the  winds  have  increased  in  velocity.  The  force  of 
the  winds  is  indicated  by  the  closeness  of  the  isobars.  The  barometer  at  the 
center  has  fallen  to  29  inches.  The  air  is  crowding  rapidly  in  from  all  sides 
and  streaming  upward.  It  whirls  as  it  rises,  and  warm,  damp  air  from  the 
Gulf  and  Atlantic  is  mixed  with  cold  air  from  the  interior  of  the  continent. 
Damp  air  is  cooled  by  expansion  and  mixture,  and  condensation  takes  place, 
resulting  in  cloudiness  almost  everywhere,  rain  in  the  southeast  quarter, 
and  snow  in  the  north  and  west.  The  southerly  winds  have  raised  the 
temperatures  in  the  southeastern  states  10  to  20  degrees  above  those  of 
the  previous  day.  The  high  on  the  Pacific  coast  has  expanded  and  de- 
veloped until  it  covers  the  western  half  of  the  country,  the  pressure  at  its 
center  in  Wyoming  being  30.9  inches.  The  slope  to  the  east  is  steep,  and 
high  northwest  winds  carry  freezing  temperatures  to  New  Mexico.  The 
central  and  southern  states  are  dotted  with  cold-wave  warnings,  which 
mean  that  the  temperature  will  fall  20  to  40  degrees  in  the  next  twenty-four 
hours. 


2o6  PHYSICAL  GEOGRAPHY 

On  January  30  the  principal  low  center  has  moved  to  the  southern 
coast  of  New  England.  Across  the  middle  of  the  country  a  ridge  of  very 
high  pressure  extends  north  and  south,  with  steep  and  regular  slopes  to  the 
ocean  on  both  sides.  Another  low  is  coming  in  from  the  Pacific.  The 
winds  have  a  high  velocity  almost  everywhere.  In  the  east  they  are  in 
accordance  with  the  slopes,  but  in  the  west  they  are  more  irregular  on 
account  of  the  influence  of  the  mountains.  A  large  area  of  snowfall  ex- 
tends from  Wisconsin  to  Maine  and  as  far  south  as  Virginia.  Over  the 
west  of  the  country  clear,  cold  weather  prevails,  with  temperatures  from 
—30°  at  Winnipeg  to  below  freezing  in  the  Gulf  and  southern  border 
states.  The  highest  temperatures  are  in  Florida  and  along  the  Pacific 
coast.     The  cold-wave  warnings  have  been  shifted  to  the  Atlantic  coast. 

On  January  31  the  storm  center  has  disappeared  over  the  Gulf  of  St.  Law- 
rence, and  the  ridge  of  high  pressure  has  moved  a  few  hundred  miles  east- 
ward. The  cold  wave  has  reached  the  extremity  of  Florida,  and  nearly 
the  whole  country  is  left  with  clear,  cold,  dry,  pure,  and  invigorating  air. 
The  rain,  snow,  and  high  winds  have  washed  dust  from  the  air  and  from 
houses,  and  the  cold  air  under  high  pressure  has  crowded  foul  gases  out  of 
every  crack  and  cranny.  At  the  same  time,  the  low  temperatures  and 
blinding  snowstorms  in  the  northern  states  bring  more  or  less  hardship 
and  danger  to  man  and  beast,  and  sometimes  blockade  railroads  for  many 
days.  Freezing  temperatures  in  the  southern  states  may  do  vast  damage 
to  fruit  orchards.  On  the  whole  the  benefit  is  probably  much  greater  than 
the  loss  or  injury.  The  procession  of  lows  and  highs  renders  the  weather 
very  variable,  bringing  a  change  from  relatively  cool,  clear,  and  dry  to 
relatively  warm,  cloudy,  and  rainy  weather,  or  the  reverse,  two  or  three 
times  a  week. 

Weather  Forecasts  and  Warnings.  —  The  United  States  Weather 
Bureau  issues  forecasts  of  the  weather  every  morning,  which  are  pubHshed 
in  the  principal  newspapers  and  posted  at  post  offices  throughout  the 
country.  Responsible  persons  who  promise  to  post  the  forecasts  in  a 
public  place  may  receive  them  on  request  free  of  charge;  some  news- 
papers publish  also  the  weather  map.  They  constitute  the  most  trust- 
worthy predictions  of  the  weather  that  can  be  made,  because  they  are  based 
upon  actual  knowledge  of  the  atmospheric  conditions  which  prevail  over 
the  continent  and  surrounding  oceans.  The  forecasts  are  made  for  large 
areas  and  cannot  prove  correct  in  every  detail  at  every  locality.  The 
eastward  movement  of  lows  and  highs  is  sometimes  slower  and  sometimes 
faster  than  usual.  Rarely  a  storm  center  moves  backward  to  the  west  for 
a  short  distance.  Occasionally  an  area  of  low  pressure  divides  or  dies  out 
or  a  new  one  is  rapi'ily  formed,  and  such  events  cannot  be  foreseen. 


, 


MOISTURE   IN  THE  AIR 


207 


Storm  warnings  are  displayed  at  all  sea  and  lake  ports  for  the  guidance 
of  mariners  and  shippers,  and  thus  great  loss  of  Hfe  and  property  is  pre- 
vented. Notice  of  the  advance  of  a  cold  wave  is  given  12  to  36  hours 
before  it  arrives,  and  in  consequence  millions  of  dollars'  worth  of  property 
is  protected  and  saved.  Frost  and  flood  warnings  are  issued  whenever 
occasion  requires  for  the  benefit  of  fruit  growers,  river  men,  and /owners  of 
property  along  streams. 

Hurricanes.  —  In  tropical  and  temperate  latitudes  Cyclonic 
storms  occur  of  such  violence  as  to  be  among  the  most  destructive 
of  natural  agencies.  Some  of  them  are  so  small  as  to  permit 
their  whirling  motion  to  be  generally  recognized,  and  are  called 
"cyclones"  in  popular  speech.  In  late  summer  and  autumn  the 
West  Indies  are  visited  by  destructive  hurricanes  which  arrive 
from  the  southeast.  They  begin  in  the  equatorial  calms  and 
increase  in  size  imtil  they  reach  a  diameter  of  100  to  300  miles 
(Fig.  181).  On  the  land  they  destroy  almost  everything, — 
forests,  crops,  buildings,  and  people.  On  the  sea  they  are  very 
dangerous  to  shipping  and  pile  up  the  water  until  it  sweeps 
over  the  coast  lands,  flooding  fields  and  towns. 


Fig.  i8i.  — Path  of  the  Galveston  hurricane. 


Fig.  182.  —Paths  of  West  Indian 
hurricanes. 


When  they  approach  the  coast  of  the  United  States  they  usually  turn  to 
the  northeast  and  die  away  in  the  north  Atlantic  Ocean  (Fig.  182).  Occa- 
sionally a  hurricane  turns  westward  near  Florida  and  passes  over  the  land, 
as  did  the  one  which  destroyed  the  city  of  Galveston,  Texas,  in  October,  1900 
(Fig.  181).     Similar  storms  occur  in  the  Pacific  Ocean  near  the  Philippine 


208 


PHYSICAL  GEOGRAPHY 


Islands,  and  in  the  Indian  Ocean  both  north  and  south  of  the  equator. 
In  those  regions  they  are  called  typhoons. 

Tornadoes. — The  tornado  or  "cyclone"  of  the  western  and 
southern  states  is  even  more  violent  than  the  hurricane,  but 

fortunately  much  smaller.  It  ap- 
pears as  a  whirling,  funnel-shaped 
cloud,  the  small  end  of  which 
sweeps  the  ground  and  overturns 
or  carries  away  everything  in  a 
path  from  a  few  rods  to  a  half 
mile  in  width.  The  wind  some- 
times reaches  a  velocity  of  200 
miles  an  hour  and  nothing  mova- 
ble can  resist  it.  Although  many 
stories  of  its  power  are  appar- 
ently incredible,  it  is  difficult  to 
exaggerate  the  truth.  Trees  of 
all  sizes  are  uprooted  or  twisted 
off,  buildings  are  demolished  and 
their  fragments  scattered  over  the 
neighborhood.  Boulders,  masses 
of  iron,  and  even  railroad  engines, 
are  lifted  from  their  places.  Ani- 
mals and  human  beings  are  whirled 
about  and  carried  long  distances, 
often  being  torn  in  pieces  or  killed 
by  collision  with  other  objects. 
Wires  and  straws  driven  into  hard  wood  testify  even  more 
strongly  to  the  incredible  violence  of  the  wind. 

The  tornado  travels  about  40  miles  an  hour  and  seldom  lasts  more  than 
two  hours.  The  average  number  in  the  United  States  is  about  150  a  year. 
They  are  most  frequent  in  Kansas,  Iowa,  Missouri,  lUinois,  and  Georgia, 
but  may  occur  anywhere  east  of  the  meridian  of  100°  and  south  of  the 
parallel  of  45°.  In  some  states  people  dig  holes  in  the  ground,  called 
"  cyclone  cellars,"  into  which  they  may  retreat  for  safety  on  the  approach 
of  a  tornado. 


Fig.  183. — Progress  of  a  tornado.  New 
castle.  Neb.,  April  30,  1898. 


MOISTURE  IN  THE  AIR 


209 


M>.     ,^^^\ 


^-im 


'M 

Tx^-^s-^^ 

j# 

jS 

M 

gS^brp^^^ 

wm 

fPflpiSP^^^ 

M 

I^^^S 

Fig.  184.  —  Efifects  of  a  tornado,  Minnesota. 

Thunderstorms.  —  Thunderstorms  are  seldom  cyclonic,  but 
result  from  the  rapid  rising  of  currents  of  warm  air  until  heavy 
cumulus  clouds  are  formed  at  the  top.  They  bring  violent 
gusts  and  squalls  of  wind  and  a  downpour  of  rain,  which  leave 
the  air  cool,  clear,  and  bracing.  In  the  United  States  a  thunder- 
storm moves  eastward  at  the  rate  of  20  to  50  miles  an  hour,  and 
grows  larger  as  it  progresses.  It  may  attain  a  length,  from  side 
to  side,  of  100  miles,  and  a  breadth,  from  front  to  rear,  of  30  miles, 
and  continue  from  2  to  12  hours. 

Rainfall.  —  There  is  probably  no  spot  on  the  face  of  the  earth 
where  it  never  rains  or  snows.  The  mean  annual  rainfall,  as 
far  as  measured,  varies  from  less  than  one  inch  to  more  than 
400  inches.  Less  than  10  inches  in  any  region  means  a  desert 
or  tundra.  At  least  20  inches  are  generally  necessary  for  forests 
and  for  agriculture  without  irrigation.  The  lands  most  favor- 
able for  human  occupation  have  from  20  to  60  or  80  inches  (Fig. 
185),  while  100  inches  or  more  may  be  counted  as  undesirable 
excess. 

Even  a  small  amount  of  rain  falling  during  the  growing  season  is  of 
more  value  for  grass  and  crops  than  a  large  amount  falling  in  the  autumn 
and  winter.  A  good  crop  of  corn  has  been  raised  in  Kansas  with  a  rainfall 
of  only  eight  inches  for  the  year,  but  most  of  it  fell  in  spring  and  early 


^ 


More  than  60  in. 
20  to  60  in. 


210 


S,  RAINFALL 


10  to  20  in. 

than  10  in. 


212  PHYSICAL  GEOGRAPHY 

summer.  Winter  rains  supply  ground  water,  fill  wells,  springs,  and  streams, 
and  saturate  the  subsoil  from  which  trees  draw  most  of  their  water  supply. 
On  a  map  showing  regions  of  small  (less  than  20  inches),  medium  (20  to  60 
inches)  and  large  (more  than  60  inches)  rainfall  (Fig.  185)  several  general 
laws  of  rainfall  appear. 

Laws  of  Rainfall.  —  i.  Disregarding  small  patches,  the  prin- 
cipal rainfall  regions  extend  north  and  south,  cutting  across  the 
temperature  zones.  This  is  due  to  the  fact  that  the  large  land 
masses  extend  north  and  south  across  the  path  of  the  prevailing 
winds. 

2.  The  coasts  of  the  continents  receive  more  rain  than  the  interior, 
and  windward  coasts  receive  more  than  leeward.  Most  of  the 
rainfall  is  first  evaporated  from  the  oceans,  carried  as  vapor  by 
the  winds,  and  condensed  as  it  is  cooled  by  rising  over  the  lands. 

3.  Highlands  act  as  screens  which  stop  most  of  the  moisture 
on  the  windward  side  and  cut  it  of  from  the  regions  on  the  lee- 
ward side,  producing  a  rain  shadow,  just  as  opaque  bodies  cut 
off  light  and  cast  dark  shadows. 

4.  In  the  equatorial  zone  as  a  whole,  the  rainfall  is  much  heavier 
than  in  higher  latitudes.  This  is  the  result  of  two  causes.  Air 
at  a  temperature  of  70°  can  contain  and  carry  nearly  twice 
as  much  vapor  as  air  at  50°,  and  more  than  four  times  as  much 
as  air  at  30°  (see  table,  p.  194).-  Warm,  damp  air  is  lighter 
than  cool,  dry  air,  and  is  compelled  to  rise  by  the  pressure  of 
heavier  air  around  it,  and  by  rising  the  vapor  is  cooled  and  con- 
densed. Somewhere  between  the  tropics,  swinging  north  and 
south  with  the  changing  position  of  the  sun  in  the  heavens,  is  the 
heat  equator  (Figs.  159,  160),  or  line  passing  through  the  point  of 
highest  temperature  on  each  meridian.  The  heat  equator  car- 
ries with  it  a  belt  of  calms  and  rising  air,  in  which  copious  rain 
falls  in  the  afternoon  and  evening  every  day.  This  belt  of  daily 
rains  crosses  the  geographical  equator  twice  a  year,  and  touches 
the  northern  tropic  in  July  and  the  southern  in  January.  Thus 
the  regions  of  heavy  rainfall  stretch  across  the  lands  from  tropic 
to  tropic,  and  have  one  or  two  rainy  seasons,  each  of  which 
lasts  a  month  or  more.    During  the  rest  of  the  year  the  trade 


MOISTURE   IN   THE   AIR  213 

winds  blow,  bringing  more  or  less  rain  from  the  ocean  to  east 
coasts  and  slopes  and  unprotected  lands  of  the  interior  (Figs.  186, 
187).  Where  the  trade  winds  blow  from  large  land  masses  or 
over  highlands  they  bring  a  dry  season,  or  in  some  cases  a 
desert  is  the  result.  In  monsoon  regions,  like  southeastern  Asia 
from  India  to  Japan,  the  winds  bring  rain  from  the  ocean  in 
summer. and  dry  weather  from  the  land  in  winter  (Figs.  186,  187). 

5.  The  subtropical  zones,  as  a  whole,  receive  less  rainfall  than 
any  other  part  of  the  land,  outside  the  polar  regions,  and  may  he 
called  the  desert  belts.  This  is  due  in  part  to  the  high  pressure 
which  exists  there,  especially  in  winter.  The  general  move- 
ment of  the  air  is  downward  and  outward  to  the  north  and 
south.  Descending  air  is  warmed  by  compression  and  hence 
cannot  bring  rain.  In  north  Africa  and  southwestern  Asia, 
the  winds  blow  from  Eurasia  and  are  dry.  Here  the  Sahara, 
Arabian,  and  Persian  deserts  stretch  from  the  Atlantic  to  India, 
covering  an  area  larger  than  the  whole  of  Europe.  In  south- 
western United  States  and  northern  Mexico,  desert  conditions 
are  intensified  and  extended  by  mountain  ranges  which  shut  out 
the  moisture  from  the  Pacific  and  Gulf  of  Mexico.  In  South 
America  the  deserts  of  Peru  and  Chile  are  rendered  almost  rain- 
less by  the  lofty  chain  of  the  Andes  on  the  east.  The  Kalahari 
desert  in  southwest  Africa  and  the  desert  of  central  Australia 
lie  in  the  rain  shadow  of  the  highlands  on  the  east. 

6.  In  the  temperate  zones  the  prevailing  winds  from  the  west 
bring  copious  rains  to  the  west  coasts  of  North  America,  Europe, 
southern  South  America,  and  New  Zealand.  In  central  Europe 
the  rains  extend  halfway  across  the  continent,  but  in  northern 
Europe  and  North  and  South  America  they  are  stopped  by 
mountain  ranges  near  the  coast. 

7.  The  eastern  half  of  North  America,  from  the  Gulf  to  Hudson 
Bay,  is  saved  from  being  a  desert  by  the  cyclonic  winds  which  bring 
rain  from  the  Gulf  and  Atlantic.  The  interior  of  North  America 
is  dry  because  the  high  mountains  shut  out  rain  from  the  west, 
and  the  cyclonic  winds  from  the  southeast  lose  most  of  their 


2l6  PHYSICAL  GEOGRAPHY 

moisture  before  they  reach  so  far  inland.  Central  Eurasia  is 
dry  because  it  is  too  far  from  the  Atlantic,  and  the  monsoon 
rains  from  the  Indian  and  Pacific  are  shut  out  by  lofty  moun- 
tains, which  inclose  the  deserts  of  Tibet,  Gobi,  and  the  Ural- 
Caspian  basin. 

8.  The  polar  caps  have  little  rainfall  because  the  air  is  too  cold 
to  carry  much  vapor. 

About  half  of  all  the  land  receives  too  little  rainfall  to  sup- 
port more  than  a  scanty  population.  Only  about  one  third  of 
the  land  receives  between  20  and  60  inches  of  rain,  the  amount 
most  favorable  for  thriving,  civilized  communities. 

The  maps  of  seasonal  rainfall.  Figs.  186,  187,  show  that  very 
few  places  in  the  world  receive  heavy  rainfall  in  winter. 


CHAPTER  XV 

CLIMATE 

Factors  of  Climate.  —  Climate  includes  all  those  conditions  of 
the  atmosphere  which  affect  plant  and  animal  hfe,  among  which 
temperature  and  moisture  are  the  prime  factors.  The  presence 
of  dust  and  disease  germs  affects  the  healthfulness  of  the  air  and 
forms  a  factor  of  cUmate.  The  cHmate  of  any  region  is  deter- 
mined by  its  latitude,  relief,  prevaiHng  winds,  and  position  in 
relation  to  the  great  features  of  land  and  sea,  and  is  thus  a 
resultant  and  expression  of  all  the  physical  influences  and  con- 
ditions which  exist  there.  It  is  mainly  cHmate  which,  in  turn, 
controls,  directly  or  indirectly,  the  Hfe  of  plants,  animals,  and 
men.  Therefore  cKmate  may  be  regarded  as  the  middle  Hnk 
in  the  chain  of  geographical  causes  and  consequences.  It  fur- 
nishes the  key  to  a  full  understanding  of  geographical  conditions. 

The  Equatorial  or  Tropical  Zone.  —  In  equatorial  lowlands 
the  temperature  is  constantly  high  with  small  range,  and  the 
rainfall  is  generally  heavy.  As  the  belt  of  calms,  with  low 
pressure  and  ascending  air,  follows  the  vertical  rays  of  the  sun 
northward  and  southward,  it  brings  a  rainy  season  in  spring 
and  fall  near  the  equator  and  in  summer  near  the  tropics.  Near 
the  equator  the  two  rainy  seasons  may  overlap,  and  on  high- 
lands exposed  to  trade  winds  from  the  ocean  the  rainfall  is  well 
distributed  throughout  the  year. 

Equatorial  regions  where  all  seasons  are  sufficiently  wet  are  occupied  by 
dense  evergreen  forests  (Figs.  192,  193).  In  regions  where,  on  account  of 
elevation  or  protection  by  highlands,  the  rainfall  is  moderate  or  there  is  a 
strongly  marked  dry  season,  the  forests  thin  out  or  disappear  and  give 
place  to  savannas  covered  with  coarse  grass  and  scattered  trees  (Fig.  200). 
In  the  monsoon  region  of  southeastern  Asia  there  is  a  hot  summer  with 
heavy  rainfall,  and  a  cool,  dry  winter.  The  monsoon  forests  are  almost  as 
luxuriant  as  the  equatorial,  but  are  nearly  leafless  in  winter. 

217 


2l8  PHYSICAL  GEOGRAPHY 

The  Subtropical  Zones.  —  In  the  subtropical  zones  of  high 
pressure  and  descending  air,  and  extending  into  the  temperate 
zones,  vast  tracts  of  arid  lands  occupy  about  half  the  land  surface 
of  the  globe.  On  account  of  the  dryness  and  clearness  of  the 
air,  arid  regions  are  subject  to  extremes  of  temperature,  the 
deserts  of  Africa,  Arabia,  North  America,  and  Austraha  being 
the  hottest  regions  of  the  world.  The  daily  range  is  sometimes 
from  above  ioo°  in  the  daytime  to  near  freezing  at  night. 

In  the  deserts  vegetation  is  confined  to  scattered  thorny  bushes  which 
are  often  leafless  (Figs.  191,  192,  204,  205).  The  deserts  are  bordered  by 
savannas  or  steppes,  where  a  thin  growth  of  bunch  grass  furnishes  pasturage 
(Figs.  192,  201,  202,  203).  The  soil  needs  only  water  to  make  it  productive, 
and  wherever  sufficient  ground  water  exists  oases  of  dense  vegetation  arise 
(Fig.  206). 

Mediterranean  Climates.  —  Some  regions  in  or  near  the  belt  of 
tropical  calms  have  a  cUmate  which  is  transitional  between  that 
of  the  subtropical  zone  and  that  of  the  temperate  zone.  The 
rainfall  is  generally  small,  but  not  so  Httle  as  to  produce  desert 
conditions.  The  summers  are  too  dry  to  be  favorable  for  grass, 
and  pasturage  is  relatively  poor.  Frost  rarely  occurs,  and  the 
range  of  temperature  is  small.  The  climate  is  characterized 
by  uniformly  mild,  dry  weather,  free  from  sudden  or  great 
changes.  The  skies  are  generally  clear,  and  warm  days  alternate 
with  cool  nights. 

In  these  regions  people  can  live  most  of  the  time  out  of  doors,  and  the 
climate  is  probably  the  most  agreeable  and  healthful  in  the  world.  Hence 
they  are  noted  as  health  and  pleasure  resorts.  These  conditions  prevail  in 
most  of  the  coast  lands  and  islands  of  the  Mediterranean  Sea,  and  con- 
stitute what  is  often  called  the  Mediterranean  climate. 

Conditions  similar  to  those  of  the  Mediterranean  region  prevail  in  CaH- 
fornia,  central  Chile,  south  Africa,  and  southwest  Australia  (Fig.  188). 

The  Temperate  Zones.  —  The  so-called  temperate  zone  in 
the  northern  hemisphere  is  broken  up  by  the  land  masses  and 
mountains  into  regions  which  have  diversified  and  even  strongly 
contrasted  climates.  Nearly  all  parts  of  North  America  and  Asia 
between  30°  and  50°  N.  Lat.  are  characterized  by  hot  summers 


CLIMATE  219 

and  cold  winters,  less  than  half  the  year  being  really  temperate. 
The  interiors  of  North  America  and  Eurasia  have  an  extreme 
continental  climate  of  great  range  of  temperature  and  small 
rainfall,  which,  in  areas  screened  by  mountains,  is  so  intensified 
as  to  produce  bleak  steppes  and  deserts  almost  as  barren  as  the 
Sahara  (Fig.  192).  The  mid-continental  ranges  of  temperature 
are  carried  by  the  prevailing  westerly  winds  over  the  east  coast 
lands  of  North  America  and  Asia,  but  cyclonic  winds  from  the 
Gulf  of  Mexico  and  Atlantic  and  the  summer  monsoons  from 
the  Pacific  bring  a  moderate  rainfall  (Figs.  185,  186). 

East  Coast  Climates.  —  Those  parts  of  the  United  States  and 
southern  Canada  lying  east  of  the  meridian  of  100°  have  a  con- 
tinental climate  with  four  strongly  marked  seasons  and  a  large 
range  of  temperature  (Figs.  161,  164).  On  the  Gulf  coast  these 
conditions  are  modified  by  nearness  to  the  ocean  and  the  tropic. 
Throughout  the  region  the  climate  is  made  changeable  by  the 
frequency  of  cyclones  and  anticyclones,  especially  in  winter,  when 
alternations  of  cold,  clear  weather,  and  mild,  cloudy  weather  with 
rain  or  snow,  occur  every  three  or  four  days. 

Northwest  winds,  blowing  out  from  an  advancing  center  of  high  pres- 
sure, bring  a  cold  wave  with  zero  temperatures  as  far  south  as  St.  Louis  and 
Philadelphia,  and  freezing  temperatures  in  Florida.  Southerly  winds  blow- 
ing toward  a  center  of  low  pressure  carry  cloud  and  rain,  changing  to  snow 
in  the  north,  across  the  country  to  and  beyond  the  Great  Lakes  (Figs.  177- 
180).  These  irregular  changes  are  very  noticeable  in  spring,  when  alter- 
nations of  almost  summer  weather  with  wintry  spells  occur  from  March 
to  May.  In  summer  the  cyclonic  changes  are  much  feebler  and  less  fre- 
quent. In  autumn  the  change  of  seasons  is  more  gradual  than  in  spring, 
and  clear,  mild  days  and  frosty  nights  may  persist  without  notable  storms 
until  December. 

Almost  ever3rwhere  east  of  the  meridian  of  100°  the  annual 
rainfall  is  above  20  inches,  increasing  from  northwest  to  southeast 
to  above  50  inches  on  the  Gulf  coast.  It  is  well  distributed 
throughout  the  year,  with  a  maximum  in  spring  and  early  sum- 
mer when  crops  are  growing.  Midsummer  and  early  autumn 
are  usually  dry  and  favorable  for  harvest  (Figs.  185,  186,  187). 


220  PHYSICAL   GEOGRAPHY 

Most  of  this  region  was  originally  covered  with  a  heavy  forest  of  decidu- 
ous trees,  green  in  summer  and  bare  in  winter.  Toward  the  north  and  on 
the  Appalachian  highlands  the  forests  are  partly  or  wholly  of  evergreen 
coniferous  trees  (Fig.  192).  Towards  the  west  the  forests  pass  gradually 
into  prairies,  or  tracts  on  which  grasses  form  a  dense,  continuous  sod  or  turf, 
trees  being  absent  except  along  the  streams. 

In  Asia  the  countries  which  most  nearly  resemble  eastern  United  States 
in  climate  and  products  are  Manchuria,  Korea,  northern  China,  and  Japan. 

West  Coast  Climates.  —  The  west  coast  lands  of  North 
America  and  Europe  are  exposed  to  the  westerly  winds  from 
the  ocean  and  have  a  truly  temperate,  oceanic  climate,  almost 
as  equable  as  that  of  the  equatorial  zone.  The  narrow  strip 
of  country  between  the  mountains  and  the  Pacific  in  Alaska, 
British  Columbia,  Washington,  and  Oregon  has  a  mild,  moist 
climate,  with  heavy  precipitation  in  winter  (Figs.  185-187).  In 
the  north  the  summers  also  are  rainy  and  the  snowfall  is  sufficient 
to  maintain  large  glaciers  upon  all  the  mountains.  The  strip  is 
covered  with  dense  forests  of  pine,  fir,  spruce,  cedar,  and  redwood, 
which  yield  a  greater  value  of  timber  to  the  square  mile  than  any 
other  in  the  world  (Fig.  192). 

The  countries  of  western  Europe  belong  to  the  same  climatic 
belt  as  the  Pacific  states  of  America.  They  are  exposed  to  the 
westerly  winds  blowing  from  the  north  Atlantic,  the  waters  of 
which  are  abnormally  warm  for  their  latitude  on  account  of 
the  drift  of  the  Gulf  Stream  from  tropical  regions.  The  winds 
themselves  are  the  chief  cause  of  the  ocean  drift,  and  are  there- 
fore both  directly  and  indirectly  the  cause  of  the  mild  climate. 
Their  influence  is  greatest  on  the  west  coast  and  diminishes 
gradually  inland,  but  south  of  Norway  there  are  no  mountains 
to  shut  out  moisture  from  the  interior. 

In  winter  the  winds  are  stronger  and  more  southwesterly  in  direction,  and 
the  isotherms  extend  almost  north  and  south,  the  temperature  decreasing 
from  west  to  east  (Figs.  160, 171,  172).  The  range  of  temperature  is  small, 
and  the  rainfall  large,  with  excess  in  autumn  and  v/inter.  The  air  is  con- 
stantly damp,  and  rain  falls  on  more  than  half  the  days  in  the  year.  In 
autumn  and  winter  fog  and  drizzHng  rain  prevail.  The  winds  from  the 
ocean  and  the  cloudiness  combine  to  prevent  great  or  sudden  changes  of 


CLIMATE  221 

temperature.  Cyclones  and  anticyclones  pass  across  these  countries  from 
west  to  east,  but  bring  much  smaller  contrasts  of  weather  than  in  eastern 
America.  Spells  of  freezing  weather  are  not  prolonged  or  severe,  and 
occasional  falls  of  snow  on  the  lowlands  do  not  remain  long  upon  the 
ground.  Hardy  plants  blossom  out  of  doors  all  winter,  and  work  in  the 
fields  can  be  carried  on  every  month  in  the  year.  The  frequent  rains  are 
very  favorable  for  grass,  which  covers  unplowed  ground  with  a  thick  sod 
even  among  the  trees  of  the  forest.  The  country  looks  fresh  and  green  at 
all  seasons.  The  Mediterranean  countries  have  a  climate  like  that  of  Cali- 
fornia, the  British  Isles  like  that  of  Oregon  and  Washington,  and  Norway 
resembles  British  Columbia  and  southern  Alaska.  The  small  range  of  tem- 
perature and  large  rainfall,  with  excess  in  autumn  and  winter,  change  gradu- 
ally eastward  to  continental  conditions  of  large  range  and  small  rainfall,  with 
excess  in  summer.  In  general  the  climate  of  central  Europe  resembles  that 
of  eastern  United  States,  with  the  direction  of  east-west  change  reversed.  A 
person  traveling  from  France  to  central  Russia  would  notice  the  same  kind 
of  changes  as  in  traveling  from  Maryland  to  Colorado,  A  traveler  from 
southern  France  to  Sweden  would  experience  changes  similar  to  those  from 
Florida  to  Quebec.  The  natural  vegetation  and  cultivated  crops  of  Europe 
have  about  the  same  range  as  in  the  United  States,  with  local  variations. 

Climate  and  Civilization.  —  The  middle  latitudes  of  North 
America,  Europe,  and  eastern  Asia  are  the  homes  of  the  most 
advanced  and  progressive  peoples  of  the  world.  The  climate 
is  not  oppressive  and  overpowering  as  in  the  equatorial  and 
polar  regions.  The  contrast  of  seasons  is  stimulating  to  human 
effort,  which  must  be  expended  in  the  summer  to  provide  food 
and  shelter  for  the  winter,  while  the  winter  brings  a  period  of 
comparative  leisure  and  rest.  The  energy  received  from  the  sun 
can  be  utilized  to  greater  advantage  than  elsewhere  to  supply 
human  wants.  Conditions  of  cHmate  and  vegetation  are  more 
capable  of  human  control  than  in  the  regions  of  perpetual  heat 
or  perpetual  cold,  and  human  intelligence  and  labor  bring  a 
greater  return  of  wealth  than  anywhere  else  in  the  world. 

In  the  southern  hemisphere  the  only  lands  which  resemble  the  United 
States  and  Europe  in  climate  and  products  are  Chile,  Argentina,  Uruguay, 
eastern  Australia,  and  New  Zealand.  Their  natural  resources  and  future 
possibilities  are  great,  but  for  the  most  part  they  lack  development  for  the 
want  of  sufl&cient  population. 


222  PHYSICAL   GEOGRAPHY 

Cold  Temperate  Zones.  —  The  northern  cold  temperate  zone 
extends  across  North  America  and  Eurasia.  The  climate  is  that 
of  continental  lands  in  high  latitudes.  The  winter  tempera- 
tures are  the  lowest  in  the  world,  except  in  Antarctica;  the  sum- 
mers are  cool  and  the  range  of  temperature  is  very  large  (Figs. 
159,  160,  161).  The  long  days  of  summer,  during  which  the 
period  of  sunshine  varies  from  16  to  24  hours,  compensate  for 
the  low  altitude  of  the  sun  above  the  horizon,  and  days  with 
temperatures  above  70°  occur.  The  growing  season  is  short,  but 
may  be  warm  enough  to  ripen  wheat  even  on  the  Arctic  circle. 
The  rainfall  is  generally  less  than  20  inches  (Fig.  185),  but  Is 
more  efficient  than  an  equal  amount  in  lower  latitudes  because 
evaporation  is  less.  During  more  than  half  the  year  the  ground 
is  covered  with  snow,  which  plays  an  important  part  in  protect- 
ing the  roots  of  trees  from  severe  frost. 

A  belt  of  coniferous  forest  extends  across  the  continents  from  ocean  to 
ocean,  interrupted  by  patches  of  "  muskeg  "  swamp  and  prairie  (Figs.  192, 
197,  199). 

In  the  southern  cold  temperate  zone,  the  narrow  extremity  of  South 
America  presents  two  strongly  contrasted  regions.  The  west  coast  re- 
sembles southern  Alaska  in  small  range  of  temperature,  heavy  rainfall,  and 
dense  coniferous  forest.  In  Tierra  del  Fuego  the  climate  is  stormy  and 
inclement  at  all  seasons,  and  snow  falls  every  month  in  the  year.  East  of 
the  mountains  the  rainfall  is  too  scanty  for  forests,  and  Patagonia  is  an 
arid  steppe  (Fig.  185). 

The  Polar  Caps.  —  In  the  north  polar  regions  the  climate  is 
still  more  severe  than  in  the  cold  temperate  zones.  The  winters 
are  not  colder  but  longer,  and  the  cool  growing  season  is  reduced 
to  two  months  or  less.  During  the  winter  the  sun  does  not  rise 
at  all  for  a  period  of  from  one  day  to  six  months.  The  sky  is 
generally  clear,  but  violent  storms  of  wind  are  frequent.  There 
is  no  spring,  but  winter  holds  with  sHght  mitigation  until  June, 
when  the  ice  begins  to  break  up  and  summer  comes  on  with 
a  rush.  The  summers  are  cold  and  foggy,  and  in  September 
winter  sets  in  again  with  full  severity.  The  annual  precipita- 
tion is  less  than  10  inches,  but  there  is  so  little  melting  that  on 


CLIMATE  223 

moderate  elevations  snow  and  ice  accumulate  from  year  to  year. 
The  ground  is  permanently  frozen  to  great  depths  and  never 
thaws  for  more  than  a  few  feet  on  top. 

The  Arctic  borderlands  of  America  and  Eurasia  are  occupied  by  tundras 
(Figs.  192,  208),  where  the  only  vegetation  consists  of  lichens,  mosses,  and 
stunted  shrubs,  which  never  grow  higher  than  the  level  of  the  snow  surface 
in  winter. 

Greenland  and  Antarctica  are  buried  under  vast  sheets  of  ice,  upon  which 
no  living  thing  exists.  Bare  land  appears  around  the  shores,  where  sea- 
birds,  mammals,  and  in  the  north  a  few  thousand  Eskimos  find  means  of 
support. 

Alpine  Climate.  —  The  climate  of  lofty  mountains  and  plateaus 
resembles  that  of  the  polar  caps.  Between  the  tropics,  surfaces 
above  about  15,000  feet  in  elevation  are  covered  with  permanent 
snow  and  ice.  In  middle  latitudes  perpetual  snow  descends  .to 
about  10,000  feet,  and  in  polar  regions  nearly  to  sea  level.  The 
height  of  the  snow  line  varies  not  only  with  the  temperature 
but  with  the  amoimt  of  snowfall,  and  is  different  on  the  wind- 
ward and  leeward  sides,  and  on  north  and  south  slopes,  of  the 
same  range.  The  rainfall  generally  increases  with  the  altitude 
to  a  height  which  varies  on  different  mountains  and  then  dimin- 
ishes. The  belt  of  heaviest  rainfall  below  the  snow  line  is  gen- 
erally forested  (Fig.  198). 

Tropical  plateaus  between  5,000  and  13,000  feet  in  elevation 
are  generally  more  healthful  and  suitable  for  human  occupation 
than  the  lowlands.  In  the  northern  Andes  and  Mexico  nearly 
all  the  cities  and  areas  of  dense  population  are  found  upon  the 
highlands.  In  Mexico  the  traveler  can  ascend  in  a  distance 
of  100  miles  from  the  hot,  damp  coast  land  to  a  temperate 
plateau  and  cold  mountain  heights,  through  as  many  belts  of 
climate  as  he  would  traverse  in  traveling  from  the  tropic  to  the 
polar  circle. 

Climatic  Regions.  —  The  map,  Fig.  188,  shows  how  the  land  areas  may 
be  divided  into  regions  bounded  approximately  by  isotherms  and  lines  of 
equal  rainfall,  in  each  of  which  the  principal  factors  of  climate  are  nearly 
uniform.    These  are  grouped  under  twelve  types,  and  all  the  regions  be- 


224 


CLIMATE  225 

longing  to  the  same  type,  wherever  they  occur,  have  essentially  the  same 
climate.  This  map  should  be  compared  with  the  maps  of  temperature 
belts  and  of  annual  and  seasonal  rainfall  (Figs.  164,  185,  186,  187).  The 
following  table  explains  the  map  and  briefly  characterizes  each  type. 

1.  Equatorial  and  Tropical.  —  All  seasons  hot  and  range  small. 
Amazon  Type.  —  Equatorial.     Rainfall  above  60  inches.     No 

dry  season.     Am.  i  -Am.  3. 

Caribbean  Type.  —  Tropical.  Rainfall  generally  20  to  60 
inches  (except  in  5).     Dry  winter.     Car.  i-Car.  5. 

2.  Subtropical  and  Warm  Temperate.  —  Alv^^ays  temperate  or 
with  a  hot  season. 

Arizonan  Type.  —  Always  dry.  Rainfall  generally  less  than 
10  inches.     Ar.  i-Ar.  5. 

Calif ornian  Type.  —  Dry  summer.  Rainfall  generally  20  to  60 
inches.     Cal.i-Cal.  5. 

Mexican  Type.  —  Dry  winter.  Rainfall  generally  less  than  60 
inches.     Mex.  i-Mex.  4. 

Floridan  Type.  —  No  dry  season.  Rainfall  less  than  80  inches. 
Fl.  1-FL5. 

3.  Temperate  and  Intemperate.  —  Temperate,  with  a  cold 
season,  or  with  a  cold  and  a  hot  season. 

Oregon  Type.  —  Oceanic.  Small  range.  Rainfall  generally 
20  to  60  inches.     Or.  i-Or.  3. 

Mississippian  Type.  —  Continental.  Large  range.  Rainfall  20 
to  60  inches.     Miss,  i -Miss.  4. 

Interior  Type.  —  Continental.  Large  range.  Rainfall  less 
than  20  inches.     Int.  i-Int.  3. 

4.  Cold  Temperate.  —  Cold  with  a  temperate  season. 
Alaskan   Type.  —  Oceanic.     Small  range.     Rainfall  in  some 

parts  above  60  inches.     Al.  i-Al.  3. 

Canadian  Type.  —  Continental.  Large  range.  Rainfall  mostly 
less  than  20  inches.     Can.  i-Can.  2. 

5.  Polar  and  Alpine.  —  Always  cold. 

Polar  Type.  —  Rainfall  generally  less  than  10  inches.  Pol.  i  - 
Pol.  4. 


CHAPTER  XVI 
PLANT   REGIONS 

The  Distribution  of  Plants.  —  The  distribution  of  plants  over 
the  face  of  the  earth  and  the  kind  of  vegetation  found  in  any 
region  are  nicely  adjusted  to  a  combination  of  conditions,  of 
which  air,  light,  water,  soil,  and  temperature  are  the  most  im- 
portant. Green  plants  absorb  about  75  per  cent  of  their,  weight 
from  the  air  in  the  form  of  oxygen  and  carbon  dioxide.     The 


Fig.  X89.  —  Zonal  arrangement  of  plants. 

absorption  of  carbon  dioxide  is  done  by  the  leaves  and  other 
green  parts  in  the  sunlight  and  cannot  take  place  in  the  dark. 
Plants  absorb  from  the  soil  through  their  roots  large  quantities 
of  water  containing  compounds  of  nitrogen,  potash,  phosphorus, 

226 


PLANT   REGIONS 


227 


lime,  and  other  elements  in  solution.  Most  of  the  water,  after 
circulating  through  the  plant,  evaporates  from  the  leaves.  For 
all  plants  there  is  a  certain  range  of  temperature  within  which 
they  are  able  to  survive,  and  a  smaller  range  within  which  they 
grow  vigorously.  Hence  plants  are  arranged  in  zones,  roughly 
corresponding  to  the  zones  of  temperature.  Within  the  zones 
of  temperature  the  distribution  of  plant  societies  is  determined 
largely  by  the  available  soil  water.  Thus  the  variations  of  soil 
water  break  up  the  plant  zones  into  plant  regions,  just  as  the 
rainfall  breaks  up  the  temperature  zones  into  climatic  regions. 
The  natural  vegetation  of  any  region  is  a  striking  and  intel- 
ligible expression  of  the  physical  conditions  of  structure,  relief, 
and  climate  which  prevail  there,  and,  consequently,  of  the  natu- 
ral influences  exerted  upon  animal  and  human  activities.  Vege- 
tation is  a  key  which  unlocks  the  chain  of  geographic  causes 
and  consequences. 

Water  Plants.  —  A  large  class  of  plants  flourish  only  in  water  or  in 
very  wet  soil,  (i)  Floating  or  submerged  plants  are  characterized  by  thin 
walls  through  which  water  is 
absorbed  by  all  parts  of  the 
plant.  Roots,  being  unneces- 
sary, are  absent  or  used  for 
anchorage  only.  The  plant  is 
supported  by  the  water,  and 
has  no  need  of  stiffness;  hence 
it  is  soft  and  flexible.  Nu- 
merous species  of  seaweed  be- 
long to  this  class,  some  of 
which  attain  such  dimensions 
as  to  rival  the  largest  of  land 
plants.  Bladderworts  and 
duckweeds  are  common  float- 
ing plants  in  fresh-water  lakes 
and  ponds.  (2)  Many  plants 
are  rooted  to  the  soil,  but 
have  submerged  or  floating 
leaves;  for  example,  pondweeds  and  water  lilies.  The  submerged  leaves  are 
commonly  narrow  and  threadlike;  the  floating  ones  very  broad  (Fig.  190). 


Fig.  190.  —  Water  plants. 


228 


PHYSICAL  GEOGRAPHY 


Fig.  191.  — Drouth  plants.    Barrel  cactus,  Mexico. 


(3)  Swamp  or  marsh  plants  are  rooted  in  water  or  very  wet  soil,  while 
their  stems  and  leaves  are  exposed  to  the  air.  Many  societies  of  them 
are  common  in  temperate  climates;  among  them  may  be  found  cat- tail 
flags,  reed  grass,  sedges,  willows,  alders,  tamarack,  and  cypress. 

Drouth  Plants  are  adapted 
to  thrive  in  a  dry  soil*  and 
climate.  They  generally  have 
an  extensive  root  systerh  in 
proportion  to  the  size  of  the 
plant,  a  small  leaf  surface, 
and  a  thickened  epidermis. 
Many  plants  survive  regular 
periods  of  drouth  by  the  dis- 
appearance of  root,  stem,  and 
leaves,  and  the  reduction  of 
the  individual  plant  to  seeds, 
bulbs,  or  tubers.  The  shed- 
ding of  leaves  is  a  provision 
against  destruction  by  the  dry 
as  well  as  the  cold  season. 
The  reduction  of  the  leaves  to 
threads  or  needles,  as  in  the 
pine  and  other  species  of  co- 
niferous trees,  and  the  total 
absence  of  leaves,  as  in  the 
cactus,  are  efficient  means  of 
withstanding  drouth.  The  perfection  of  these  adaptations  is  probably 
found  in  the  melon  cactus,  in  which  the  whole  plant  is  reduced  to  a  spiny, 
thick-skinned,  globular  mass. 

Intermediate  Plants.  —  The  class  of  plants  adapted  to  a  medium  sup- 
ply of  water  comprises  about  80  per  cent  of  all  known  forms  and  consti- 
tutes the  more  common  vegetation  of  temperate  regions. 

Salt  Plants.  —  Some  species  of  plants  are  able  to  grow  where  the  soil 
water  is  impregnated  with  common  salt  or  alkali,  which  would  be  fatal  to 
most  plants.  Salt  plants  are  found  along  the  seashore,  in  tidal  marshes, 
around  salt  lakes,  and  in  arid  regions. 

Plant  Regions.  —  The  land  surface  may  be  divided  according 

to  its  vegetative  covering  into  woodland,  grassland,  and  desert. 

I .    Woodland.  —  Trees  are   deep-rooted  and  their  growth  is 

not  dependent  on  frequent  rain  or  a  rainy  growing  season,  but 


PLANT  REGIONS  229 

on  the  presence  of  water  within  reach  of  the  deep  roots.  They 
require  a  warm  growing  season,  a  moist  subsoil,  and  calm,  damp 
air  in  winter.  They  may  thrive  where  long  seasons  of  drouth 
recur  periodically.  They  are  not  limited  by  low  temperature 
in  winter,  if  protected  by  a  snow  covering,  but  suffer  from  dry 
winds  when  the  ground  water  is  frozen. 

2.  Grassland.  —  Grasses  are  shallow-rooted  and  their  growth 
is  dependent  upon  a  moist  superficial  soil.  They  require  fre- 
quent, even  if  small,  rainfall  during  the  growing  season.  They 
endure  extreme  drouth  during  the  season  of  rest. 

3.  Desert.  —  Deserts  are  due  to  dryness  of  the  ground  or  low 
temperature.  Except  on  ice  caps,  vegetation  is  not  absent  but 
sparse.  There  is  always  much  vacant  space,  and  the  plants  do 
not  struggle  against  one  another  for  room,  but  against  unfavorable 
conditions  of  soil  and  climate.  Fig.  192  shows  the  distributidh 
of  the  principal  types  of  vegetation.  It  should  be  compared 
with  the  map  of  climatic  regions  (Fig.  188). 

Wet  Woodland.  —  Tropical  Rain  Forest.  —  In  the  climatic 
regions  of  the  Amazon  type,  where  the  temperature  is  constantly 
high  and  the  rainfall  above  60  inches,  the  growth  of  vegetation 
is  luxuriant.  Dense  forests  of  very  tall  trees,  overgrown  with 
climbing  plants  and  air  plants,  and  crowded  with  underbrush, 
occupy  the  country  and  almost  shut  out  large  animals  and  men. 
The  trees  have  large,  thin  leaves  with  smooth,  glossy  skin  to 
shed  water,  and  are  green  all  the  year  round.  The  number  of 
species  growing  together  is  very  large,  but  palms  and  tree  ferns 
are  characteristic.  This  woodland  can  hardly  be  penetrated 
except  by  way  of  the  streams,  and  is  more  difficult  to  cross  than 
a  desert. 

If  men,  with  great  labor,  make  a  little  clearing  in  it  to  plant  crops,  the 
native  vegetation  springs  up  again  so  rankly  that  the  work  of  clearing 
must  be  done  over  again  every  year.  The  heavy  rainfall  leaches  and 
washes  away  the  soil,  which  is  soon  exhausted.  The  hot,  damp  air  is  un- 
healthful  and  oppressive,  and  the  scattered  inhabitants,  overcome  by  the 
forces  of  nature,  are  unable  to  rise  above  a  state  of  savagery.  These  con- 
ditions prevail  in  a  large  part  of  the  Amazon  basin,  in  west  equatorial 


H  H    H    O 


230 


PLANT  REGIONS 


231 


Africa,  and  in  the  East  Indies.  European  peoples  have  made  some  prog- 
ress in  establishing  colonies  in  all  these  regions,  and  have  stimulated  the 
natives  to  gather  and  grow  valuable  tropical  products,  such  as  rubber, 
sugar,  coffee,  spices,  chocolate,  tapioca,  tobacco,  fruits,  oils,  and  medicines. 


mj^r-t 


m^ 


WW 


Pm. 


Fig.  193. — Tropical  rain  forest,  Java. 


Monsoon  Forests.  —  In  some  parts  of  the  monsoon  region  of 
southeastern  Asia  the  rainfall  is  more  than  60  inches,  but  occurs 
mostly  in  summer,  while  the  winters  are  relatively  cool  and  dry. 
In  the  rainy  season  the  forests  are  much  Hke  the  tropical  rain 
forest,  but  in  the  dry  season  are  leafless. 

Temperate  Rain  Forest.  —  In  the  cHmatic  regions  of  the 
Floridan  type  the  conditions  are  similar  to  those  of  the  tropical 
rain  forest,  except  that  the  temperatures  are  not  so  high  and  the 
rainfall  is  not  so  heavy.  They  are  occupied  by  a  mixed  forest 
of  evergreen  and  deciduous  trees.  Climbing  and  air  plants, 
ferns,  and  tree  ferns  are  abundant.  The  multiplicity  of  species 
is  very  great.  The  camphor  tree  of  Formosa,  the  eucalyptus  of 
Australia,  and  the  palmetto  and  live  oak  of  Florida  are  charac- 
teristic.    These  forests  are  much  less  formidable  than  the  tropi- 


232 


PHYSICAL  GEOGRAPHY 


cal  rain  forests.  They  have  been  largely  cleared  and  the  lands 
now  support  a  moderate  or  dense  population  of  civilized  people. 
The  principal  crops  are  rice,  corn,  wheat,  sugar  cane,  cotton, 
semi-tropical  fruits,  and,  in  China,  tea. 


l^-ii-ijcmte  rain  forest,  Florida. 


Temperate  Summer  Forest.  —  The  climatic  regions  of  the 
Oregon  and  Mississippian  types  are  very  favorable  to  the  growth 
of  trees  which  have  broad,  soft,  thin  leaves  in  summer  and  are 
bare  in  winter.  The  oak,  beech,  maple,  elm,  chestnut,  ash, 
linden,  and  sycamore  are  characteristic  and  widely  distributed. 
Climbing  plants  and  air  plants  are  rare,  but  grasses  and  herba- 
ceous plants  growing  among  the  trees  are  relatively  abundant. 

These  forests  furnish  the  world's  supply  of  hardwood  timber  for  fuel 
and  construction.  In  the  United  States  and  Europe  they  have  been  largely 
destroyed  to  clear  the  land  for  agriculture.  The  combination  of  forest 
and  grassland,  natural  or  artificial,  affords  good  conditions  for  agriculture 


PLANT  REGIONS 


233 


and  stock  raising,  and  makes  these  regions  preeminent  in  the  production 
of  foodstuffs  and  the  homes  of  the  richest  and  most  progressive  peoples. 


Fig.  195.  —  Temperate  summer  forest,  North  Carolina.     (U.S.G.S.) 


Dry  Woodland.  —  Tropical  Dry  Forest.  —  In  the  climatic  re- 
gions of  the  Calif  ornian  type  and  some  of  the  Mexican  type  trees 
grow  in  clumps  rather  than  in  forests.  The  leaves  are  ever- 
green, small  and  thick,  with  a  leathery  skin.  The  myrtle,  holly, 
laurel,  box,  cork  oak,  oleander,  cypress,  and  olive  are  character- 
istic species.  Lilies,  tulips,  hyacinths,  and  other  herbaceous 
plants  growing  from  bulbs  and  tubers  are  numerous.  Grass  is 
scanty  and  poor,  and  sheep  and  goats  are  kept  in  preference 
to  cattle.  In  the  Mediterranean  region  olive  oil  largely  takes 
the  place  of  meat  and  butter.  Grapes  and  tropical  fruits 
flourish,  while  grain  is  grown  in  the  cool,  moist  season  or  by 
means  of  irrigation. 

The  plateau  of  the  Dekkan  (Mex.  4,  Fig.  188)  is  protected  by  bordering 
heights  from  the  excessive  monsoon  rains.  Two  or  more  crops  a  year  are 
often  raised,  some  suitable  to  the  hot,  wet  season  (June  to  October),  and 


234 


PHYSICAL  GEOGRAPHY 


others  to  the  cool,  dry  season  (November  to  March).    Thus  the  same  area 

may  produce  large  crops  of  wheat,  rice,  and  cotton.    The  monsoon  rains  are 

so  variable  from  year  to  year 
that  the  crops  often  fail,  and 
on  account  of  the  dense  pop- 
ulation a  dry  year  may  bring 
a  serious  famine  in  which 
thousands  starve  to  death. 
Irrigation  is  practiced,  and 
India  is  dotted  with  storage 
tanks  and  wells.  About  50,000 
miles  of  canals  carry  off  flood 
waters,  and  in  the  dry  season 
distribute  water  to  the  fields. 
Extreme  forms  of  tropical 
dry  forest  are  thorn  forest  and 
thorn  scrub,  in  which  all  woody 
plants  are  dwarfed,  scraggy, 
thorny,  and  tangled,  forming 
thickets  difficult  to  penetrate 
(Fig.  196).  The  dwarf  oak, 
acacia,  and  mesquite  are  char- 
acteristic. Thorn  forests  occur 
in  scattered  patches  in  the 
borderlands    around    deserts 

and  grasslands.    It  is  called  chapparal  in  North  America,  catinga  in  Brazil, 

and  scrub  in  Australia  (Fig.  203). 

Temperate  Dry  Forest  {Coniferous) .  —  Climatic  regions  of  the 
Alaskan  and  Canadian  types  are  generally  occupied  by  ever- 
green coniferous  forests.  Most  of  the  species  have  a  central 
trunk,  with  horizontal  or  pendent  branches  in  whorls,  and  their 
fruit  is  a  cone.  The  needle-shaped  or  scale-shaped  leaves, 
with  a  hard  skin,  are  adapted  to  dry  and  frozen  soils  and  strong 
winds.  The  pine,  fir,  spruce,  cedar,  and  larch  extend  through- 
out the  cold  temperate  belts  and  on  mountain  sides  in  all  lati- 
tudes, and  furnish  the  world's  supply  of  soft-wood  timber. 

The  valuable  products  are  timber,  as  yet  largely  unavailable  for  want  of 
means  of  transportation,  and  the  furs  of  numerous  small  animals,  such  as 


^J^ 

1 

^^^rj[fT^S 

vSsBf^^st'* 

*  '"'Iw^wlP 

ppH^^p**^^^ 

Fig.  196. — Tropical  dry  forest,  Mexico. 


Fig.  197.  —  Coniferous  forest,  Great  Bear  Lake,  Canada. 


Fig.  198. — Spruce  forest,  Colorado. 
235 


236 


PHYSICAL  GEOGRAPHY 


the  fox,  sable,  marten,  mink,  otter,  badger,  beaver,  and  muskrat.     Canada 
and  Siberia  have  been  for  centuries  the  chief  sources  of  furs,  and  there  is 

no  indication  that  the  supply 
is  diminishing.  The  popula- 
tion is  generally  very  sparse. 
Coniferous  forests  sometimes 
occur  on  poor,  porous  soils, 
in  wet,  warm  regions,  as  the 
long-leaved  pine  of  the  south- 
ern United  States 

Grassland.  —  Savanna. 
—  In  climatic  regions  of 
the  Caribbean  type,  the 
vegetation  consists  chiefly 
of  tall,  stiff  grasses  grow- 
ing in  dense  tufts.  Low, 
deciduous  trees  with  par- 
asol-shaped tops  are  scat- 
tered about  and  give  the 
landscape  a  parklike  as- 
pect (Fig.  200).  A  large 
part  of  central  Africa  is 
occupied  by  such  savan- 
nas, the  home  of  immense 
numbers  of  large  ani- 
mals,— ^the  elephant,  rhi- 
noceros, hippopotamus, 
giraffe,  lion,  leopard,  buf- 
falo, zebra,  and  nearly 
It  is  the  finest  country  in 


Fig.  199.  —  Cedar  forest,  Oregon.    (U.S.G.S.) 


one  hundred  species  of  antelopes 
the  world  for  ''  big  game." 

The  abundance  of  animal  life  has  been  a  serious  hindrance  to  human 
occupation  and  control,  but  is  itself  an  evidence  of  what  might  be  done 
there  with  domestic  animals.  The  success  of  native  agriculture,  carried  on 
with  rude  implements  and  methods,  in  raising  corn,  bananas,  millet,  beans, 
sheep,  goats,  and  cattle,  suggests  great  possibilities  for  the  future.  Under 
the  control  of  Europeans  the  black  natives  are  prevented  from  robbing  and 


PLANT  REGIONS 


237 


killing  one  another,  and  are  settling  down  into  peaceful  and  orderly  in- 
dustrial communities.  The  natural  conditions  are  favorable  for  their 
redemption  from  primeval  savagery  and  for  the  occupation  of  the  country 
by  civilized  peoples. 


Fig.  200.  —  Savanna  with  fringing  forest.  East  Africa. 

A  part  of  Brazil  is  a  plateau  with  moderate  rainfall,  and  the 
forests  are  replaced  by  campos,  or  undulating  grassy  tracts, 
with  clumps  of  trees  in  the  valleys.  In  Venezuela  the  rain 
shadow  of  the  Guiana  highlands  produces  the  llanos,  which 
have  a  warm,  rainless  winter  of  five  months,  during  which  all 
vegetation  apparently  dies.  When  the  summer  rains  appear 
grass  and  herbaceous  plants  spring  up  and  grow  luxuriantly. 
In  swampy  depressions  and  along  streams  oases  of  stunted  trees 
rise  like  islands  from  the  sea. 

Prairie.  —  In  the  drier  parts  of  climatic  regions  of  the  Mis- 
sissippian  type,  forests  give  place  to  prairies,  or  open  tracts  of » 
meadow,  covered  with  a  thick,  continuous  sod  of  grasses  and 
other  herbaceous  plants.  Fringing  forests  of  small  trees  along 
the  streams  do  not  occupy  more  than  20  per  cent  of  the 
area.  The  soil  is  especially  fertile  and  easily  worked.  Such 
lands  lie  all  ready  for  human  occupancy,  and  are  at  once  avail- 
able with  small  expenditure  of  labor.  The  American  prairies 
are  one  of  the  most  productive  agricultural  regions  in  the  world. 

Steppe.  —  Climatic  regions  of  the  Interior  type,  and  other 


^38 


PHYSICAL  GEOGRAPHY 


temperate  regions  with  a  rain- 
fall between  lo  and  20  inches, 
are  covered  with  bunch  grass, 
which  does  not  form  a  con- 
tinuous sod  or  grow  very 
high.  It  cures  on  the  ground 
into  a  nutritious  hay.  Trees 
are  very  rare.  Vast  areas  of 
this  kind  exist  in  the  interior 
of  Eurasia,  where  they  are 
called  steppes.  They  have 
been  for  many  centuries  the 
home  of  nomad  peoples,  who 
have  no  fixed  habitation,  but 
wander  about  with  flocks  and 
herds  of  cattle,  horses,  camels, 
sheep,  and  goats  in  search  of 
pasture.  The  similar  regions 
of  North  America  have  been  ranged  over  by  herds  of  cattle 
under  the  care  of  "cowboys,"  but  are  now  being  divided  up 
and  fenced  into  cattle  and  sheep  ranches.     By  irrigation  and 


iviiS-^A'-^ 


Fig.  201.  — Bunch  grass.    (U.S.G.S.) 


Fig.  202. — Steppe,  South  Dakota.    (U.S.G.S.) 


PLANT   REGIONS 


239 


dry  farming  agriculture  is  generally  encroaching  upon  the  areas 
of  pasture. 

The  pampas  of  Argentina 
include  prairie  and  steppe 
lands,  hitherto  used  for  rais- 
ing sheep  and  cattle  for  wool 
and  hides.  As  railroads  are 
extended  they  are  being  con- 
verted into  wheat  fields.  The 
veldt  of  the  Transvaal,  in 
South  Africa,  is  a  similar  re- 
gion, where  cattle  raising  is 
combined  with  some  agricul- 
ture (Fig.  203).  The  Austra- 
lian hush  between  the  desert 
and  the  eastern  mountains, 
belongs  to  the  same  class,  and 
supports  millions  of  sheep  Pig.  203.— Steppe  and  thorn  scrub,  South  Africa, 
and    cattle.       Steppe    lands 

are  "  belts  of  herbage  strown  between  the  desert  and  the  sown,"  and  will 
always  be  important  sources  of  meat,  wool,  and  hides. 


Fig.  204.  —  Sage  brush  desert,  Arizona. 


Deserts.  —  In  desert  regions  the  rainfall  is  generally  less  than 
10  inches,  but  desert  conditions  may  occur  where  the  rainfall 
is  much  larger  if  rapid  evaporation  or  subterranean  drainage 


240 


PHYSICAL  GEOGRAPHY 


leaves  the  soil  and  subsoil  too  dry.      Great  deserts  occur  in  cli- 
matic regions  of  the  Arizonan,  Interior,  and  Polar  types. 

Warm  Deserts.  —  In  tropical  and  temperate  deserts  vegeta- 
tion is  limited  to  drouth  and  salt  plants  only.     The  root  system 

is  large  and  shallow,  and  the 
leaf  surface  is  greatly  re- 
duced. There  are  few  leaves 
at  once,  and  in  many  forms 
no  leaves  at  all,  their  func- 
tions being  performed  by  the 
stems.  Desert  plants  re- 
spond quickly  to  a  slight  fall 
of  rain,  and  pass  through 
their  stages  of  leaf,  flower, 
and  fruit  rapidly.  They  are 
characterized  by  thick  skin, 
hairs,  spines,  resins,  and 
spongy  tissue  for  storing 
water.  The  cactus,  agave, 
sage  brush,  and  creosote  bush 
are  typical  forms.  Where 
sufficient  ground  water  ex- 
ists, permanently  or  tempo- 
rarily, oases  occur  and  sup- 
port a  sparse  population. 
The  air  of  the  desert  is 
pure  and  stimulating,  and 
acts  directly,  along  with  the 
hard  conditions  of  life,  to  render  animals  and  men  lean,  hardy, 
restless,  and  fierce. 

Polar  and  Alpine  Deserts.  —  Along  the  polar  borders  of  con- 
iferous forests  and  above  the  timber  line  on  mountains,  the 
growing  season  is  short  and  plant  growth  is  very  rapid.  Patches 
of  herbaceous  plants  have  rosettes  of  leaves  next  to  the  ground 
and  send  up  short  stems  bearing  bright-colored  flowers.     Trees, 


Fig.  205.  —  Giant  cactus,  Arizona. 


PLANT  REGIONS 


241 


Fig.  206.  —  Date  palm  oasis,  Sahara.    Note  flat-roofed  houses. 

when  present,  are  stunted,  scraggy,  and  twisted.     Shrubs  spread 
out  close  to  the  ground  in  dense  mats. 

Tundras.  —  In  high  latitudes  and  altitudes  the  ground  is  per- 
petually frozen,  thawing  only  to  the  depth  of  a  few  inches  in 


Fig.  207.  —  Alpine  desert,  Bolivia. 


242 


PHYSICAL  GEOGRAPHY 


summer.  The  principal  vegetation  consists  of  lichens  and  mosses, 
upon  which  caribou,  reindeer,  musk  oxen,  and  hares  find  sub- 
sistence.   Willows,  larches,  and  junipers  occur  in  the  form  of 


Fig.  208.  —  Tundra,  Lapland. 

dense  cushions,  which  do  not  rise  above  the  level  of  the  snow 
surface  of  winter. 

Ice  Deserts.  —  Ice  caps  are  entirely  devoid  of  vegetation,  ex- 
cept the  occasional  appearance  of  microscopic  algas  known  as 
''  red  snow." 

In  cold  deserts  the  possibilities  of  human  life  are  reduced  to  the  lowest 
limits.  In  Europe  the  Laplanders  maintain  a  semicivilized  life  by  keeping 
herds  of  reindeer.  In  Asia  the  Chukchis,  and  in  America  the  Eskimos, 
depend  largely  upon  the  sea,  in  which  fish,  birds,  seals,  and  walrus  abound. 


\ 


CHAPTER  XVII 
THE    GEOGRAPHY    OF   ANIMALS 

Water  Breathers  and  Air  Breathers.  —  The  most  important 
distinction  among  animals  due  to  adaptation  to  geographical 
environment  is  that  between  those  which  absorb  oxygen  from 
solution  in  water  and  soon  die  out  of  water,  and  those  which 
absorb  oxygen  from  the  air  and  soon  die  when  immersed  in 
water.  The  conditions  of  life  in  the  water  are  more  simple 
and  less  varied  than  in  the  air.  The  water  furnishes  nearly 
uniform  pressure  on  all  sides  of  the  body,  and  little  energy  is 
expended  in  supporting  weight;  hence  the  form  and  surface  of 
the  body,  the  structure  of  the  skeleton  and  muscular  system, 
and  the  character  and  arrangement  of  the  limbs  are  adapted  to 
propulsion  through  the  medium.  A  comparison  of  a  fish  and  a 
cat  will  show  a  remarkable  contrast  in  these  particulars.  The 
water  breathers  include  all  fish,  most  shellfish,  such  as  oysters 
and  clams,  most  crustaceans,  such  as  crabs  and  lobsters,  and  a 
vast  number  of  lower  and  less  familiar  forms  of  animal  life. 
The  temperature  of  water  is  uniform  over  wide  areas,  and  far 
less  changeable  than  that  of  the  air.  Food  supply  is  more  gen- 
erally diffused  in  water  than  on  land,  and  many  aquatic  animals 
are  fixed  to  one  spot  and  have  their  food  brought  to  them  by 
currents.  Hence  the  water  breathers  belong  entirely  to  the  less 
highly  developed  classes.  The  demands  upon  them  are  compara- 
tively few  and  simple,  and  their  lives  do  not  require  the  numerous 
and  complex  activities  and  abilities  of  life  in  the  air. 

Marine  animals  depend  directly  or  indirectly  for  food  upon 
the  vegetation  which  flourishes  in  the  sea  or  the  organic  mat- 
ter brought  by  rivers  from  the  land.     Life  in  the  sea  is  most 

243 


244 


PHYSICAL  GEOGRAPHY 


abundant  in  the  shallow  waters  of  the  continental  shelf  (p.  24), 
which  are  penetrated  by  the  heat  and  light  of  the  sun,  and 
where  the  bottom  is  covered  with  mud  from  the  land.  The 
open  sea  is  inhabited  near  the  surface  by  great  schools  of  fish 
and  swarms  of  invertebrate  animals,  many  of  which  are  minute 
in  size.  The  abundance  of  mineral  matter  in  solution,  the  vol- 
ume of  sunhght,  and  the  uniformity  of  temperature  are  favor- 
able to  the  growth  of  microscopic  plants  in  such  numbers  as  to 
furnish  an  ample  food  supply  for  all. 

The  sea  is  probably  rather  densely  inhabited  at  aU  depths,  but  those 
animals  which  live  constantly  below  a  few  hundred  feet  are  difficult  to 
catch,  and  our  knowledge  of  them  is  imperfect.     Deep-sea  animals  exist 


Fig.  209.— Deep-sea  fish,  with  lanterns. 


under  conditions  of  great  pressure,  low  and  unchanging  temperature,  and 
absolute  darkness.  Most  of  them  are  degenerate  descendants  of  surface 
and  shallow  water  forms.  Some  are  eyeless  and  some  are  provided  with 
lantern  organs  which  generate  a  dim  light.  Owing  to  the  great  area  and 
depth  of  inhabited  waters,  the  number  of  marine  animals  probably  exceeds 
all  others. 

Some  animals  are  amphibious,  spending  a  part  of  their  lives  in  water 
and  a  part  in  the  air.  Many  insects  are  hatched  and  pass  their  larval 
stage  in  water,  but  live  their  adult  life  in  air.  Tadpoles  have  gills  and  are 
true  water  breathers,  but  change  into  frogs,  toads,  or  salamanders,  which 
are  air  breathers.  A  few  animals  have  both  gills  and  lungs  throughout  life 
and  can  live  in  either  medium.  Among  the  higher  animals  some  assume 
the  aquatic  form  and  habit,  but  are  not  water  breathers.     Among  birds  the 


THE   GEOGRAPHY  OF  ANIMALS 


245 


Fig.  210.  —  Marine  mammals. 

penguins  swim  vigorously  under  water 
in  pursuit  of  fish.  Even  some  mam- 
mals, which  suckle  their  young  and 
cannot  Hve  more  than  a  few  minutes 
under  water,  have  assumed  the 
aquatic  form  and  habit.  Such  are  the 
whale,  dolphin,  porpoise,  sea  cow, 
seal,  and  walrus.  The  last  two  are 
ice-riding  animals,  vigorous  swimmers 
which  spend  a  part  of  the  time  on  the 
polar  ice. 

Fliers  and  Walkers.  —  An- 
other distinction  among  animals, 
scarcely  less  important  geo- 
graphically,  is   the   division  of 


Fig.  211.  —  Penguins.  Wings  are  used  for 
swimming.  (Sliackleton's  The  Heart  of 
the  Antarctic.) 


246 


PHYSICAL   GEOGRAPHY 


air  breathers  into  fliers  and  walkers  or  crawlers.  Most  birds  and 
insects  and  a  few  mammals  have  become  highly  specialized  for 
locomotion  in  the  air.  The  buoyancy  and  resistance  of  the  air 
are  slight  compared  with  water,  and  flying  requires  a  more  com- 
plex body  structure  than  swimming.  The  insect  body  is  small 
and  very  light,  with  a  thin  outer  shell,  provided  with  one  or 
two  pairs  of  delicate  wings.  The  muscles  inside  the  shell  are 
capable  of  moving  the  wings  at  a  high  speed,  amounting  in  the 
house  fly  to  330  strokes  a  second.  The  bones  of  the  bird  are 
hollow  and  filled  with  air  for  lightness,  the  fore  limbs  are  pro- 
vided with  a  complex  arrangement  of  interlocking  and  folding 
feather  vanes,  the  breast  bone  and  muscles  are  strongly  de- 
veloped for  moving  the  wings,  and  the  tail  feathers  act  as  a 

rudder. 

Among  the  more  power- 
ful birds,  flight  has  at- 
tained the  climax  of  natural 
locomotion.  The  passen- 
ger pigeon  can  fly  100  miles 
an  hour,  the  eagle  and  con- 
dor can  rise  to  great  heights 
and  soar  almost  without 
effort,  while  the  albatross 
and  frigate  bird  make  jour- 
neys of  thousands  of  miles 
across  the  sea.  Yet  no  an- 
imal can  Hve  in  the  air  indefinitely  without  alighting  on  land  or  water  for 
rest  and  food. 

Animal  Adaptations.  —  The  adaptations  of  animals  to  food 
supply,  climate,  enemies,  and  breeding  are  innumerable.  A  few 
of  the  more  striking  cases  may  be  noticed. 

Most  insects  are  vegetable  eaters  and  live  upon  the  juices  and 
leaves  of  plants.  Many  eat  dead  animal  matter  or  are  parasitic 
on  live  animals. 

The  large  majority  of  birds  live  on  seeds,  fruits,  and  insects. 
Sea  birds  are  fish  eaters,  and  birds  of  prey  catch  land  animals 
alive.    A  few  are  scavengers  of  carrion. 


Fig.  212.  —  Soaring  bird. 


THE   GEOGRAPHY  OF   ANIMALS 


247 


Mammals,  with  few  exceptions,  are  land  animals  and  walk, 

run,  or  jump.     A  few  species  swim  (p.  245).     Bats  are  the  only 

mammals  that  really  fly. 

Most  mammals  are  plant 

eaters    (herbivorous)     or 

flesh  eaters  (carnivorous) , 

but  bears,  swine,  and  men 

eat    all    kinds    of    food. 

Plant  eaters  have  cutting 

teeth  for  cropping  herb- 
age, and  flat  grinders  for 

chewing    it.      The    large 

ones  are  hoofed  animals, 

including     cattle,    sheep, 

goats,  deer,  antelopes,  the 

giraffe,  camel,  horse,  hog, 

hippopotamus,  rhinoceros, 

and  elephant.     The  small 

plant  eaters  are  gnawers 

(rodents),  such  as  the  squirrel,  prairie  dog,  beaver,  rat,  mouse, 

guinea  pig,  and  rabbit.     The  flesh  eaters  live  mostly  upon  the 

plant  eaters  and  generally  have 
claws  and  sharp  teeth  for  catching, 
holding,  and  tearing  their  prey. 
The  large  ones  are  bold  and  fierce, 
with  keen  senses  and  quick  intelli- 
gence, as  shown  by  the  cat,  lion, 
tiger,  leopard,  panther,  dog,  fox, 
wolf,  bear,  otter,  and  weasel.  The 
small  ones  live  chiefly  upon  insects, 
as  the  mole  and  the  bat.     The  plant 

eaters  in  a  wild  state  are  in  constant  danger  of  attack  from  the 

flesh  eaters,  and  few  of  them  have  adequate  means  of  defense. 

Their  safety  lies  in  flight  or  concealment;  hence  the  majority 

have  keen  senses  and  are  slender,  agile,  and  built  for  speed. 


Fig.  213.  — Plant  eater:  caribou. 


Fig,  214.  —  Flesh  eater:  lion. 


248 


PHYSICAL  GEOGRAPHY 


Fig.  215.  —  Hippopotamus.    Lives  mostly  in  water 
with  only  eyes  and  nostrils  above  the  surface. 


A  few  are  able  to  maintain  themselves  by  strength,  mass,  and 
tough  skin,  as  the  bison,  rhinoceros,  hippopotamus,  and  elephant. 

The  rodents  are  in  danger 
from  birds  as  well  as  beasts  of 
prey,  and  find  refuge  by  bur- 
rowing in  the  ground,  in  hol- 
low trees,  or  about  buildings. 
Many  animals  of  all  classes 
are  favored  by  protective  colora- 
tion which  makes  them  almost 
invisible  in  their  usual  haunts. 
Cases  of  this  kind  are  most  nu- 
merous among  insects  and  birds, 
but  the  lion  on  the  sand,  the  leopard,  zebra,  and  giraffe  in  the  forest,  and 
the  Arctic  fox,  hare,  and  ptarmigan  on  the  snow,  are  striking  examples. 

Shelter. — The  higher  animals  generally  make  use  of  some  kind 
of  a  shelter,  nest,  or  house,  at  least  for  the  purpose  of  rest  and 
rearing  their  young.  Aquatic  animals  are  generally  homeless,  but 
fur  seals  swim  hundreds  of  miles  to  reach  the  islands  where  they 
annually  congregate  to  bring  forth  their  cubs.  On  land,  animals 
burrow  in  the  ground  and  make  use  of  natural  rock  houses  or 
dens.  Beasts  of  prey  find  shelter  and  a  sleeping  place  in  some 
thicket.  The  hippopotamus  spends  the  day  in  the  water,  with 
only  his  nostrils  visible.  The  large  plant  eaters  are  generally 
homeless  and  their  young  are  ''  precocious,"  or  able  to  run 
with  their  mothers  soon  after  birth.  Constructive  abiUty 
reaches  a  high  development  among  birds,  whose  nests  are  often 
marvels  of  skill  in  the  choice  of  site  and  in  the  adaptation  of 
materials  to  home  building.  Yet  the  palm  for  such  achieve- 
ment must  be  given  not  to  any  bird,  but  to  the  beaver  and  the 
bee.  The  beaver  gnaws  down  trees,  builds  an  elaborate  dam 
with  timber  and  mud,  raises  his  house  of  reeds  above  the  sur- 
face of  the  pond,  and  enters  it  through  a  tunnel  opening  under 
water.  Bees  construct  in  a  hollow  tree  a  comb  made  of  their 
own  wax,  in  a  form  which  gives  a  maximum  of  storage  space 
with  a  minimum  of  material,  and  fill  it  with  honey  and  pollen. 


THE   GEOGRAPHY   OF   ANIMALS  249 

It  is  notable,  however,  that  such  feats  are  accompHshed  only  by 
an  organized  community  which  rivals  human  society. 

Distribution  of  Animals.  —  Animals  are  so  much  more  mobile 
than  plants  that  they  have  become  more  widely  diffused,  and 
the  earth  cannot  be  divided  into  animal  regions  so  clearly  dis- 
tinguished as  the  plant  regions.  It  may  be  said  that  every 
species  of  animal  would  be  found  in  every  part  of  the  earth 
suitable  for  its  maintenance,  if  it  were  not  prevented  by  bar- 
riers of  some  sort  which  its  individuals  are  unable  to  cross. 
The  principal  barriers  to  animal  migration  are  water,  climate, 
mountains,  deserts,  forests,  lack  of  food  supply,  and  enemies. 
Marine  animals  are  generally  limited  to  salt  water,  but  some  sea 
fish  run  up  rivers  to  spawn  and  feed.  The  barriers  in  the  sea  are 
differences  of  temperature,  pressure,  and  food  supply.  Shallow- 
water  forms  never  venture  far  into  the  open  sea  because  of  lack 
of  food.  Deep-sea  forms  die  when  brought  to  the  surface  be- 
cause of  reduction  of  pressure.  Those  which  swarm  in  warm 
surface  waters  would  perish  in  waters  a  few  degrees  colder. 

On  land  the  most  widely  distributed  animals  are  birds,  bats, 
and  some  insects  on  account  of  their  powers  of  flight.  Those  of 
smallest  range  are  found  among  fresh-water  fishes,  which  can- 
not cross  from  one  stream  system  to  another  and  are  stopped 
by  high  falls,  and  snails,  which  are  very  poor  travelers.  For 
most  land  animals  except  fliers  the  sea  is  an  absolute  barrier 
to  migration,  and  each  land  mass  would  have  a  fauna  in  most 
respects  unlike  every  other  if  there  had  never  been  any  land 
connection  with  some  other  mass.  Mountain  ranges  are  bar- 
riers more  on  account  of  climate  and  limited  food  supply  than 
height  and  steepness.  If  they  were  not  cold  and  barren  most 
animals  would  be  able  to  climb  and  cross  them.  Deserts  are 
nearly  as  efficient  barriers  as  the  sea  because  they  are  almost 
equally  foodless.  Grazing  animals  cannot  cross  a  wide  belt  of 
dense  forest  because  of  want  of  grass,  and  forest  animals  do 
not  flourish  in  grassland.  Although  warm-blooded  animals  have 
the  power  to  maintain  their  bodily  temperature  above  that  of 


250 


PHYSICAL  GEOGRAPHY 


the  surrounding  air  and  are  generally  protected  by  a  coat  of 
hair,  wool,  feathers,  or  fat,  these  things  are  not  sufficient  to 
enable  them  to  live  in  all  climates.     Domestic  cattle  would  soon 

perish  in  Greenland,  where 
the  musk  ox  seems  not  to 
suffer  at  temperatures  of 
eighty  degrees  below  zero. 
Polar  bears  brought  to  tem- 
perate regions  must  be  con- 
stantly supphed  with  ice. 

Animal  Realms.  —  The  Northern 

Realm.  —  The  northern  continents 

are  close  together,  and  in  the  past 

have  been  so  connected  as  to  give 

a  continuous  land  area  from  Nor- 

Fig.  216.  -  Musk  ox.  ^ay  eastward  around  to  Labrador. 

The  bulk  of  these  continents  hes  in  temperate  regions  between  the  tropic 

and  the  polar  circle,  and  there  is  no  impassable  north-south  mountain  bar- 


Fig.  217.  —  Animal  realms  and  regions. 


rier.  Consequently  the  fauna  throughout  this  vast  area  presents  a  striking 
similarity,  with  a  multitude  of  minor  differences.  It  is  especially  the  home 
of  the  hoofed  grass  eaters,  —  cattle,  deer,  sheep,  goats,  horses,  and  camels. 
While  beasts  of  prey  are  not  absent,  the  species  are  relatively  few  in  num- 


THE   GEOGRAPHY  OF  ANIMALS 


251 


ber  and  inferior  in  size.  These  natural  conditions  have  been  intensified  by 
man,  who  has  killed  the  flesh  eaters  and  bred  the  grass  eaters.  North 
Africa  has  recently  been  connected  by  land  bridges  with  Europe,  and  be- 
longs to  the  Northern  realm,  which 
finds  its  southern  land  boundaries 
along  the  tropic  in  the  natural 
barriers  of  the  Mexican  plateau, 
the  Sahara  and  Arabian  deserts, 
and  the  great  mountain  ranges  of 
southern  Asia. 

The  I ndo- African  Realm  lies  be- 
tween the  tropics  and  includes 
Africa  south  of  the  Sahara,  Asia 
south  of  the  Himalayas,  and  most 
of  the  islands  of  the  East  Indies. 
It  is  far  richer  in  number  and  vari- 
ety of  species  than  the  Northern 
realm.  The  plant  eaters  are  well 
represented  by  wild  cattle,  asses,  and  horses  in  Asia  and  by  antelopes 
and  zebras  in  Africa;  but  the  flesh  eaters  are  even  more  conspicuous, 


Fig.  218.  — Zebra. 


Fig.  219.  —  Chimpanzee, 


Fig.  220.  —  Qiraffes. 


252 


PHYSICAL   GEOGRAPHY 


Fig.  221.  —  Ostriches. 


including  the  lion,  tiger,  leopard,  and  panther,  the  largest  and  most  fero- 
cious of  their  class.  It  is  the  home  of  the  largest  land  animals,  —  the 
rhinoceros,  hippopotamus,  and  ele- 
phant, —  and  of  the  tallest,  —  the 
giraffe.  It  is  well  suppHed  with 
four-handed  folk,  containing  all  the 
manlike  apes,  the  gorilla,  chimpan- 
zee, and  orang,  and  all  the  tailless 
monkeys,  besides  baboons,  gibbons, 
and  lemurs.  Among  its  birds  are 
eagles,  vultures,  ostriches,  guinea 
fowls,  peafowls,  pheasants,  and  the 
jungle  cock.  Crocodiles  and  venom- 
ous serpents  abound.  More  than 
half  its  mammals  and  birds  do  not 
occur  elsewhere.  In  number,  vari- 
ety, and  beauty  of  butterflies  and 
beetles  it  is  unrivaled.  Central 
Africa  is  now  the  richest  region  in 
the  world  for  big  game,  but  white  men  will  soon  exterminate  many  of 
the  species  unless  they  are  protected  by  law. 

The  South  American  Realm  is 
almost  wholly  tropical  and  includes 
the  most  extensive  and  luxuriant 
forests  in  the  world.  Large  ani- 
mals of  the  higher  classes  are  sin- 
gularly few.  Notwithstanding  the 
existence  of  the  pampas,  llanos, 
and  campos  (pp.  237,  239),  which 
are  vast  seas  of  grass,  the  hoofed 
grass  eaters  are  poorly  represented 
by  a  few  deer,  the  llama  and  three 
other  small  species  of  the  camel 
family,  the  peccary,  and  the  tapir. 
Horses,  cattle,  and  sheep  have  been 
introduced  from  Europe.  The 
beasts  of  prey  are  the  puma,  pan- 
ther, and  jaguar,  the  latter  a  match 
for  the  lion.  Among  animals  pecul- 
Fig.  222.  —  Liaim.  iar  to  this  realm  are  the  little  arma- 


THE   GEOGRAPHY  OF   ANIMALS 


253 


dillos,  the  sluggish  sloths,  the  toothless  anteaters,  and  the  long-tailed  mon- 
keys. Yet  it  is  surpassingly  rich  in  the  lower  forms  of  life,  and  is  the  paradise 
of  naturalists.  In  birds,  reptiles, 
fishes,  and  insects  it  is  the  most  pop- 
ulous part  of  the  world.  Five  sixths 
of  the  birds  do  not  occur  elsewhere. 
There  are  400  species  of  humming 
birds.  Among  its  serpents  are  the 
anaconda  and  boa  constrictor,  the 
largest  of  their  kind;  and  turtles, 
crocodiles,  and  alligators  abound. 


Fig.  223.  —  Tapir.  Fig.  224.  —  Monkey, 

Most  of  the  animals  in  the  world  would 
thrive  in  South  America  if  they  could  get 
there. 

The  Australian  Realm,  including  Austraha, 
New  Zealand,  New  Guinea,  and  some  small 
islands,  presents  the  poorest  and  strangest 
assemblage  of  animals  in  the  world.  Most 
of  its  mammals  belong  to  the  small  and 
unique  group  which  carry  their  young  in  an 
abdominal  pouch  formed  by  a  fold  of  skin. 
The  largest  is  the  kangaroo,  as  tall  as  a 
man,  and  making  prodigious  leaps  with  its 
powerful  hind  legs  and  tail.  These  and  sev- 
eral species  of  large  and  almost  wingless 
birds,  the  emus  and  cassowaries,  are  the 
most  prominent  of  the  native  inhabitants.  Fig.  225.— Emu. 


254 


PHYSICAL  GEOGRAPHY 


i 


i 


Fig.  226.  —  Kangaroo. 


Flesh  eaters  are  represented  only  by  dogs.  These  lands  have  been  long 
separated  from  the  other  continents  by  deep  water,  which  has  kept  out  all 
the  larger  and  higher  forms,  including  beasts  and  birds  of  prey.  They  are 
a  sort  of  museum  in  which  weak  and  inferior  species,  long  ago  destroyed  in 
other  lands,  have  been  protected  from  enemies  and  preserved.  The  thor- 
oughness of  this  protection  is  shown  by  the  fact  that  rabbits  introduced 
from  Europe  have  so  multiplied  in  the  absence  of  enemies  as  to  become  a 
serious  pest. 

Islands  are  poor  in  species  of  both  animals  and  plants  in  proportion  to 
their  distance  from  the  continents.  Mammals  are  often  entirely  wanting. 
Birds  and  insects,  which  can  fly,  and  reptiles,  whose  eggs  are  not  killed  by 
salt  water,  are  more  numerous. 


CHAPTER  XVIII 

THE   HUMAN    SPECIES 

Man  as  an  Animal.  —  Compared  with  the  animals  which  are 
physically  best  equipped  for  the  struggle  for  existence,  man  is 
in  most  respects  inferior.  He  cannot  fly,  is  a  slow  and  awkward 
swimmer,  and  is  easily  outstripped  in  running.  For  defense  he 
has  no  horns,  or  hoofs,  or  beak,  or  claws,  and  his  teeth  are  small. 
His  skin  is  soft,  thin,  and  almost  naked.  The  young  require 
parental  care  for  many  years.  His  structure  indicates  descent 
from  ancestors  of  apelike  habits,  living  in  trees  and  on  fruits. 
The  physical  characters  which 
render  him  superior  to  all 
other  animals  pertain  chiefly 
to  the  feet,  hands,  and  skull. 
The  feet  and  limbs  are  used 
for  locomotion  only,  and  he 
can  stand  and  walk  erect. 
The  hands  and  arms  are 
highly  perfected  and  left  free 
for  use  solely  as  organs  for 
grasping,  holding,  and  per- 
forming delicate  and  complex 
movements.  The  skull  has 
more  than  twice  the  capacity 

of    that    of    any    ape.        Its    SU-     courtesy  of  the  university  Society. 
tures  do  not  unite  for  twenty  Fig.  227.-Negro  boy  and  apes. 

years  or  more,  thus  enabling  the  brain  to  attain  a  weight  in 
proportion  to  the  total  body  weight  four  to  thirty  times  that  of 
other  intelligent  animals.  The  long  period  of  growth,  and  the 
size  and  complexity  of  the  brain,  render  possible  a  development 
of  the  mental  powers  which  sets  the  human  species  apart  from 

255 


256  PHYSICAL  GEOGRAPHY 

all  the  other  inhabitants  of  the  earth,  and  almost  immeasurably 
superior  to  them.  With  few  exceptions,  man  is  the  only  species 
in  which  the  individuals  cooperate  in  a  complex  way  for  the 
benefit  of  the  community.  It  is  by  living  in  societies  that  man 
has  become  educated  and  civilized.  "  Man  has  not  made  so- 
ciety, but  society  has  made  man."  All  those  things  which  are 
the  result  of  human  thought  constitute  a  realm  by  itself,  which 
may  be  called  the  mind  sphere  {psychos phere) . 

Enemies.  —  Man's  worst  enemies  are  no  longer  beasts  of 
prey  and  venomous  serpents,  although  these  are  still  formidable 
in  Africa  and  India,  but  the  minute  organisms  which  infect  his 
body  with  disease.  Many  tribes  of  American  Indians  have  been 
exterminated  by  smallpox  and  measles.  To-day  parts  of  cen- 
tral Africa  are  being  depopulated  by  sleeping  sickness.  The 
plague  is  carrying  off  the  people  of  India  by  the  hundred  thou- 
sand. Asiatic  cholera  and  yellow  fever,  bred  in  the  tropics, 
have  repeatedly  carried  death  into  temperate  countries.  Ma- 
larial fever  renders  many  parts  of  the  equatorial  regions  almost 
uninhabitable  by  white  men.  Yet  no  one  of  these  diseases 
is  more  destructive  than  the  ''  white  plague  "  of  tuberculosis, 
which  causes  as  many  deaths  in  the  United  States  every  year  as 
did  the  whole  Civil  War.  All  these  diseases  and  many  more 
are  caused  by  microscopic  plants  or  animals  which  multiply  in 
the  blood,  and  have  been  unrecognized  until  recently.  Medical 
and  sanitary  science  has  discovered  means  of  defense  against 
many  of  these  enemies,  and  may  be  expected  to  conquer  all  of 
them  in  time. 

Varieties  and  Races.  —  Of  all  species  of  animals,  man  is  the 
most  widely  distributed.  His  intelligence  enables  him  to  Hve 
in  all  lands  and  all  climates  between  Greenland  and  Tier r a  del 
Fuego,  and  from  marshes  and  islands  near  sea  level  to  the  high 
Andes  and  Himalayas.  From  his  cradle  land,  which  was  prob- 
ably in  southern  Asia,  he  seems  to  have  migrated  in  all  direc- 
tions, without  definite  purpose  or  destination,  wherever  the  land 
connections  of  those  remote  times  furnished  a  road.     Led  on  by 


THE  HUMAN  SPECIES 


257 


the  pursuit  of  food,  or  driven  from  place  to  place  by  enemies, 
he  penetrated  every  unoccupied  land,  and  while  still  in  a  very 
rude  stage  of  culture  took  pos- 
session of  most  of  the  hab- 
itable world.  In  the  struggle 
for  existence  under  such  a 
great  variety  of  conditions, 
men,  like  other  animals,  nec- 
essarily developed  differently 
and  unequally.  Hence  arose 
four  distinct  races,  differing 
in  physical  and  mental  char- 
acteristics. The  hot,  moist 
equatorial  forests  of  central 
Africa  produced  a  black  race 
(Ethiopian) ,  which  spread  over 
tropical  Africa  and  the  whole 
of  Australia,  which  formed  a  new  center,  where  men  of  a  some- 
what different  and  lower  type  were  developed.     The  high,  arid 


Fig.  228.  —  Ethiopian  race. 


Fig.  229.  —  Mongolian  race. 


Fig.  230.  —  American  race. 


plateaus  of  central  Asia  produced  a  yellow  race  (Mongolian),  which 
spread  over  nearly  the  whole  of  Asia  and  the  neighboring  islands. 
The  American  continent  produced  a  red  race  (American) ,  perhaps 


258 


PHYSICAL  GEOGRAPHY 


originally  a  branch  of  the  yellow,  which  occupied  its  whole  area 
for  many  centuries  without  interference  from  the  rest  of  the 
world.     North  Africa  and  western  Europe  gave  birth  to  a  white 


Fig.  231.  —  Distribution  of  races  previous  to  modern  migrations. 

race  (Caucasian),  which,  in  historic  times,  has  ^spread  thence  over 
northern  and  southern  Asia,  America,  south  Africa,  and  Australia, 
dispossessing  or  gaining  control  of  the  aboriginal  races.  Fig. 
231  shows  the  distribution  of  the  four  races  as  it  was  previous 

to  the  modem  migra- 
tions which  began  in  the 
sixteenth  century.  The 
table  on  page  259  shows 
their  distinctive  charac- 
teristics and  present  dis- 
tribution. 

Types  of  the  Caucasian 
Race.  —  The  peoples  of 
each  race,  though  alike  in 

the  characteristics  men- 
Fig.  232. -Long  skull  and  broad  skull.  ^j^^^^^  ^^  p^^^  ^59,  differ 

in  many  minor  details.  Among  the  peoples  of  the  Caucasian 
race  there  are  three  well-marked  types,  Baltic,  Alpine  and 
Mediterranean: 


THE   HUMAN   SPECIES 


259 


•^^ 


a 
o 


^  o 
o 


O) 


PhPh 


> 


^. 


03  _;  ^ 


nd    (U    C3    (D 


-5 'Si 

5    OJT^ 


r-l  "rl  'O  .rH 


§ 

<D 

•c 

<U 

l-l 

t/3 

;h 

rj 

U 

3 

a 

Q 

» 

T3 

Ti ' 

.2  w  a;  ;S  o 


O 


i& 

;i^  03 

03   g 

cd 

o3t--h  CTj 
o    ^  >— I 


If 


U 

o  ^  o 


a- 


W)      c 

CO     .     » 

W  -^   03 

c^  w  -2   ^  03  :^  -(J 

'C    wo    tn  03    O 

>^^kJ     en 


+J  o 


^  _   03   tH 

<l^  ^      rt    t7-( 

G  03  ;r;  C 

rt  wr;:;  o3 


c  "^  ^ 


<U     ii  M- 


(^ 


2  w).2^ 

03  ,C!   w 


c  6"  03" 

rG      gxl 

5  t:  J3 

o  <u 


o 


<u 

03   O 


13  i^ 

>H« 

03 

|g 

< 

1 

0 

03 
u 

S 

0 

GXi 


Vh   o   c   o 

03rG^'-i 


CO 


rt  .- w 
>  c 

o3  Ot3 

jH   OS  c^ 
C   N 

p;^  CD 

>^ 

c5  +^    Vh 


c3 


a' 


•^^  > 


o 

i§ 


U5"H  1^  -^  ^  c 

03^03'^^   w'g,^ 

^Ph  <;  (_t  .^  0) 


P^ 


IS 
3* 


o^ 


03<i3   c^ 


'S  2  c  c 

C -^  03   c^ 

04>.?i,  o  OS 
Go-go 


o    . 

OS  o3 

"d   O 

o.;2 
►  o 

J3  >^ 


o  G  QJ  >.^ 

C  O  ^  Wits 

J3  S^  O  1^ 

o  ^  C  a  > 

w  03  >'t; 

^  43  +3  ,G    ^ 

^     r^  <D  03     O 

>i  u.  G  <1^  ® 


w   O 


<D    0) 


■•^  >iJ         G   c 

w«  oTO-C 

(1)  ^  03  ^Xi 

^4J>  ^   03    G    c/3 

crt  w  ?  ;^  __,  'r) 


"o  ci3 

Offi 


rt  >  ":<  w 


^§ 


26o 


PHYSICAL  GEOGRAPHY 


I.  Baltic.  —  Blond  or  florid,  with  flaxen  or  reddish  glossy  hair, 
blue  eyes,  long  skull,  and  tall  stature.     Scandinavians,  North 

Germans,  Dutch,  English, 
Scotch,  Irish,  and  their  de- 
scendants in  America,  Austra- 
lia, and  south  Africa;  West 
Persians,  Afghans,  many  Hin- 
dus, and  some  other  peoples 
of  southwest  Asia. 


Fig.  233.  —  Baltic  type.    Darwin. 


Fig.  234.  —  Alpine  type.     Pasteur. 

2.  Alpine. — Light  brown  or 
swarthy,  with  brown,  wavy  dull 
hair,  brown,  gray,  or  black 
eyes,  broad  skull,  and  medium 
stature.  Most  French  and 
Welsh,  South  Germans,  Swiss, 
Russians,  Poles,  Bohemians, 
and  other  peoples  of  south- 
eastern Europe ;  Armenians, 
East  Persians,  and  the  peoples  of  the  eastern  Pacific  islands. 
3.  Mediterranean,  —  Olive  brown  to  almost  black,  with  dark 


Fig.  235.  —  Mediterranean  type.  —  A  Sicilian. 


26l 


262  PHYSICAL  GEOGRAPHY 

or  black  wiry  hair,  dark  or  black  eyes,  long  skull,  and  small 
stature.  Spanish  and  Portuguese  and  their  descendants  in 
America;  some  French,  Welsh,  and  Irish;  Italians  and  Greeks; 
Berbers,  Egyptians,  and  other  peoples  of  north  Africa;  Arabs, 
Syrians,  and  other  peoples  of  southwest  Asia;  some  Hindus. 

Population  of  the  World.  —  The  population  of  the  world  has 
increased  250  per  cent  in  the  last  century,  and  now  exceeds 
1,600  milhons.  Of  these  about  51  per  cent  are  Caucasian,  36 
per  cent  MongoKan,  11  per  cent  Ethiopian,  and  i  or  2  per  cent 
American. 

The  map,  Fig.  236,  shows  that  the  large  groups  of  dense  population 
are  all  in  the  northern  continents  and  mosdy  between  the  tropic  and  the 
polar  circle.  About  75  per  cent  of  the  world's  population  live  between  the 
annual  isotherms  of  40°  and  70°;  this  is  not  wholly  due  to  the  direct  in- 
fluence of  temperature,  but  largely  to  the  difficulty  of  maintaining  human 
life  in  the  midst  of  luxuriant  tropical  vegetation.  The  most  habitable  parts 
of  the  world  lie  between  the  tropical  forests  and  deserts  and  the  cold  tem- 
perate coniferous  forests.  More  than  70  per  cent  of  the  world's  population 
live  in  regions  having  a  rainfall  between  20  and  60  inches. 

''  Man  is  a  deep-sea  inhabitant  of  an  ocean  of  air,"  and 
thrives  best  where  there  is  the  greatest  depth  of  atmosphere 
above  him.  In  1880,  93  per  cent  of  the  people  of  the  United 
States  lived  at  elevations  of  less  than  1,500  feet  above  the  sea, 
and  it  is  probable  that  the  proportion  is  not  very  different 
for  the  whole  world  to-day.  The  possibilities  of  population  in 
any  region  depend  primarily  upon  the  number  of  people  that 
can  be  fed.  .Therefore  the  highest  densities  may  be  looked  for 
in  warm  lowlands  without  excessive  rainfall,  and  in  cooler  and 
drier  lands  which  can  import  a  part  of  their  food  supply  from 
abroad.  In  such  cases  accessibility  from  the  sea  is  an  impor- 
tant factor.  The  former  conditions  are  exemplified  in  south- 
eastern Asia,  where  half  the  people  of  the  world  Hve  almost 
entirely  on  their  own  products,  and  the  latter  conditions  in 
western  Europe,  where  one  fifth  of  the  world's  population  live 
largely  by  buying  food  from  America,  eastern  Europe,  and  Asia. 


PART   II.     ECONOMIC    GEOGRAPHY 


CHAPTER  XIX 

NATURAL  RESOURCES  AND  FOOD  SUPPLY 

Natural  Resources.  —  Wherever  and  however  men  Hve,  they 
are  dependent  upon  the  natural  resources  of  the  earth  for  a 
Hving.  A  naturalist  on  the  coast  of  Australia  relates  how  he 
came  across  a  band  of  "  black  fellows,"  as  the  natives  are  called, 
at  their  camp,  or  rather  lying-down  place,  for  they  had  no  huts 
or  shelter  of  any  kind.  He  hired  them  to  show  him  the  nests 
of  a  certain  species  of  bird,  promising  to  give  them  plenty  of 
biscuit  after  they  had  shown  the  nests.  They  were  all  clothed 
in  natural  attire,  the  brown-black  skin  in  which  they  were 
born,  with  the  addition  of  a  thick  coat  of  white  clay  and  red  and 
yellow  ochre  on  their  faces  and  chests.  Each  man  carried  one 
or  two  spears,  which  he  threw  at  the  birds  flying  overhead. 
One  climbed  a  tree,  tore  off  some  onion-like  plants  growing  on 
the  upper  limbs,  and  threw  them  down  to  his  companions,  who 
ate  them  all  up  before  he  got  down  to  claim  his  share.  Along  a 
stretch  of  rocky  shore  were  many  crabs,  which  the  blacks  caught 
and  ate  raw  and  alive.  They  also  found  sea  snails  with  shells 
three  or  four  inches  long,  which  they  strung  on  a  reed  stem  to 
hang  in  the  sun  until  the  animal  should  die  and  putrefy,  so  that 
it  could  be  drawn  out  and  eaten.  Some  bulbs  like  Indian  turnip 
were  dug  up  and  tied  in  their  hair,  to  be  cooked  in  the  future. 
A  lizard  and  a  grub  six  inches  long  were  tussled  for,  torn  in 
pieces,  and  swallowed  on  the  spot.  The  nests  having  been 
found  and  the  biscuits  handed  over,  the  blacks  filled  themselves 

263 


264 


ECONOMIC   GEOGRAPHY 


and  lay  down  to  sleep.  They  cared  no  more  for  the  traveler 
or  his  biscuit.  One  had  a  short  pipe  tied  to  his  arm,  and  was 
persuaded  by  the  promise  of  tobacco  to  pilot  the  traveler  back 
to  the  shore. 

The  wants  of  these  savages  are  almost  as  simple  as  those  of 
the  animals  around  them,  and  they  exercise  but  little  more  fore- 
thought than  the  animals 
in  providing  for  them. 
The  European  colonists 
and  their  descendants  liv- 
ing in  the  same  country 
make  use  of  a  hundred 
natural  resources  of 
which  the  savages  never 
dreamed.  They  grow 
wheat,  corn,  grapes,  or- 
anges, and  other  fruit, 
raise  sheep  and  cattle,  and 
mine  coal,  gold,  copper, 
and  tin.  They  have  abun- 
dance of  bread,  meat,  and 
fruit  to  eat,  and  clothing 
to  wear.  They  use  stone, 
brick,  timber,  and  iron  in 
constructing  houses,  ve- 
hicles, and  ships.  They 
travel  with  horses,  steam 
cars,  and  automobiles. 
They  use  gold  and  silver 
for  ornament  and  coinage.  They  exchange  their  own  products 
with  all  the  rest  of  the  world  for  comforts  and  luxuries  which 
they  do  not  find  at  home.  Their  wants  increase  as  the  means 
of  supply  increase,  and  there  is  no  limit  to  the  number  of  things 
they  can  use.  Yet  the  civilized  man  is  as  dependent  upon 
natural  resources  as  the  savage. 


A 

i 

¥W  J 

m 

i 

Fig-  237.  —  Australian  natives. 


NATURAL  RESOURCES  AND   FOOD   SUPPLY  265 

Utilization  of  Natural  Resources.  —  Most  natural  resources 
must  be  worked  over  and  utilized  by  human  labor.  Crude 
minerals  are  manufactured  into  implements  and  machinery, 
soils  are  made  to  yield  food  products,  forests  are  converted  into 
houses  and  ships.  Man's  desire  to  consume  and  his  ability  to 
produce  have  increased  together  with  the  progress  of  civiliza- 
tion. The  earth  is  not  only  the  home  of  man  but  also  his 
workshop  and  school  —  a  great  "manual-training  high  school." 
While  he  has  made  it  more  habitable,  comfortable,  and  luxurious, 
it  has  made  him  civilized.  The  study  of  those  natural  resources 
which  are  useful  to  man,  and  of  the  uses  which  men  make  of 
them,  constitutes  the  science  of  economic  geography}  It  dis- 
cusses the  influence  of  natural  environment  upon  human  activi- 
ties, and  the  conscious  reaction  of  man  upon  his  environment. 
It  recognizes  the  relationship  between  nature  and  human  wel- 
fare, and  considers  how  the  earth  is  fitted  for  the  development 
of  civilization. 

The  economic  progress  of  man  means  his  ability  to  make  a  better  living, 
and  depends  upon  natural  resources  and  human  faculty.  Natural  resources 
are  practically  unchangeable  from  age  to  age,  but  man,  through  the  ex- 
perience of  thousands  of  years  and  by  his  increasing  knowledge  of  nature, 
may  improve  his  condition  indefinitely. 

Chief  Natural  Factors.  —  The  chief  natural  factors  of  eco- 
nomic geography  are  (i)  the  substratum,  or  ground,  including 
minerals,  soils,  and  ground  water,  (2)  climate,  (3)  plants,  and 
(4)  animals.  Each  of  these  factors  contributes  to  human  wel- 
fare directly,  and  also  through  its  influence  on  the  other  factors. 

Soil  and  ground  water  combine  with  climate  to  determine  the  character 
of  vegetation.  Plants  manufacture  food  for  animals,  and  both  for  man. 
Plants  and  animals  are  our  neighbors  and  kinsmen,  closely  related  to  us 
physiologically,  and  more  remotely  by  descent  from  common  ancestors. 
They  have  developed  with  man,  and  their  control  and  conquest  have  been 
comparatively  easy. 

Some  natural  resources  essential  for  the  existence  of  man  are  almost 
everywhere  present,  and  so  abundant  as  to  require  little  or  no  attention. 

^  Economy  means  literally  housekeeping,  or  household  management. 


266  ECONOMIC   GEOGRAPHY 

Among  these  are  air,  water,  insolation,  and  land.  We  live  at  the  bottom  of 
an  ocean  of  air,  which  penetrates  water  and  solid  earth  to  great  depths. 
The  supply  is  inexhaustible,  and  it  is  difficult  to  shut  it  out ;  yet  in  mines 
and  tunnels,  fans  and  pumps  are  employed  to  insure  safety,  and  in  crowded 
rooms,  houses,  and  cities  a  sufficient  supply  of  good  air  is  a  serious  problem. 
On  the  sea  and  in  deserts  the  traveler  must  continually  look  to  his  water 
supply  or  pay  the  penalty  with  his  life,  and  water  for  irrigation  is  a  costly 
commodity.  In  well-watered  regions  some  energy  and  expense  are  generally 
necessary  to  secure  good  water  for  domestic  use,  and  in  cities  one  of  the 
largest  items  of  public  expenditure  is  for  water.  Insolation,  or  radiant 
energy  from  the  sun,  penetrates  the  atmosphere,  and  furnishes  heat  and 
light  to  every  part  of  the  face  of  the  earth  during  half  of  each  year.  It 
makes  plants  grow,  enables  animals  to  live,  and  supplies  all  the  power  avail- 
able for  human  industries. 

Land,  as  terra  firma,  or  a  ground  upon  which  men  can  stand,  walk,  live, 
and  work,  is  abundant  and,  as  yet,  largely  unoccupied.  There  is  room 
enough  in  the  state  of  Texas  to  contain  all  the  people  in  the  world  and  to 
give  every  man,  woman,  and  child  a  space  as  large  as  an  ordinary  city  lot. 
Most  of  the  land  is  covered  by  some  kind  of  soil  which  is  workable  and 
fertilizable,  and  its  total  productive  capacity  is  sufficient  to  support  many 
times  the  present  population  of  the  world.  The  substratum  is  only  super- 
ficially known  and  used  except  in  mining,  which  is  limited  in  depth  to  about 
one  mile.     Its  surface  is  generally  traversable  by  roads. 

Food  Supply. — The  only  absolutely  necessary  thing  which  man 
must  procure  to  live  is  food.  A  part  of  this  is  easily  obtained 
from  the  mineral  world  in  the  form  of  air,  water,  and  common 
salt,  but  man  cannot  live  upon  mineral  food  alone.  He  must 
depend  upon  plants  to  convert  mineral  matter,  air,  water,  and 
salts  into  organic  substances  which  he  can  assimilate.  Gener- 
ally he  robs  plants  of  the  food  which  they  have  stored  up  for 
the  next  season  or  the  next  generation.  Bulbs,  thickened  roots, 
tubers,  fruits,  nuts,  and  grains  are  local  concentrations  of  food 
stuff  in  the  plant  which  form  staple  articles  of  diet  for  men 
almost  everywhere.  The  animal  body  contains  still  more  con- 
centrated food  stuff,  and  almost  every  part  of  it  except  hair, 
feathers,  and  bones  are  eaten  by  men.  Shellfish,  fish,  worms, 
reptiles,  birds,  and  all  the  higher  animals  are  caught,  hunted,  or 
bred.     Materials  provided  by  animals  for  the  support  of  their 


NATURAL  RESOURCES  AND   FOOD   SUPPLY 


267 


young,  such  as  eggs  and  milk,  are  of  special  value  because  they 
can  be  used  without  kilHng  the  animal  which  produces  them. 

Collective  Economy.  —  The  simplest  way  of  getting  a  Kving  is 
that  in  which  men  make  no  effort  to  produce  anything,  but  live 
by  plucking  or  collecting  whatever  nature  provides,  as  in  the 
case  of  the  Australian  black  fellows.  This  is,  of  course,  very 
inefficient,  but  in  tropical  countries  nature  is  so  prolific  that 
people  can  five  with  Httle  effort. 

On  the  coral  islands  of  the  Pacific  a  few  coconut  trees  will  support  a 
large  family.  No  implements,  or  only  very  simple  ones,  are  required. 
There  is  no  incentive  to  stimulate 
discovery  and  invention,  and  men 
remain  in  a  state  of  savagery. 
Tropical  forests,  savannas,  and 
oceanic  islands  are  most  favorable 
for  plant  collection  on  account  of 
the  abundance  and  variety  of  ed- 
ible fruits  and  nuts.  Various  spe- 
cies of  palms,  such  as  the  oil  palm, 
date  palm,  sago  palm,  and  coco- 
nut palm,  are  important  sources 
of  food  supply.  The  yam,  a  root 
resembling  the  sweet  potato,  and 
the  banana,  the  most  prolific  of 
all  food  plants,  flourish  sponta- 
neously and  render  labor  almost 
unnecessary. 

Fishing,  hunting,  and  trap- 
ping are  forms  of  collective 
economy  which  require  considerable  effort  and  skill.  Imple- 
ments and  weapons,  such  as  fishhooks,  lines,  nets,  spears,  har- 
poons, bows  and  arrows,  must  be  designed  and  made,  and  the 
successful  chase  of  the  larger  animals  demands  trained  powers 
of  body  and  mind. 

Hunting  furnishes  a  limited  and  precarious  food  supply,  abundant  at 
one  time  and  scanty  at  another.  A  large  territory  is  necessary  to  support 
a  few  people.    The  North  American  Indians  of  Columbus's  time  depended 


/A 

wmf^m. 

fm$ 

m 

M,   :.^ 

m 

fete' 

m 

^1 

% 

IffiiN'.^M 

^: 

%£ 

i 

Fig.  238.  —  Top  of  coconut  palm. 


NATURAL  RESOURCES  AND   FOOD   SUPPLY 


269 


upon  the  chase,  and  there  were  probably  not  more  than  one  million  of  them 
on  the  continent  north  of  Mexico.  Hunting,  trapping,  and  fishing  survive 
and  continue  among  highly  civilized  peoples.  They  are  still  the  chief  occu- 
pations in  the  great  forest  belts  of 
the  cold  temperate  zone.  Fishing  is 
carried  on  in  favorable  coast  waters 
in  all  latitudes,  but  is  most  pro- 
ductive on  both  shores  of  the  north 
Atlantic  and  north  Pacific. 

Agriculture.  —  The  domesti- 
cation of  plants  is  a  long  step 
toward  a  large  and  regular  food 
supply.  It  was  at  first  hap- 
hazard from  seed  accidentally 
sown.  The  planting  and  care 
of  cultivated  plants  was  begun 
and  carried  on  entirely  by 
women,  who  loosened  the  soil 
in  favorable  spots  with  a  stick, 

planted  seed,  and  cultivated  the  growing  crop  with  rude  hoes. 
This  was  the  beginning  of  hoe  culture,  which  now  prevails  in  the 
equatorial  forests  and  savannas  of  South  America,  Africa,  and 
the  East  Indies.     The  banana,  manioc,  and  yam  are  the  staple 

crops  (Fig.  249).     As  hoe 


Fig.  240.  —  Hoe  culture. 


m^kjiSi: 


culture  becomes  more  effi- 
cient it  develops  into 
garden  culture,  which  is 
intensive  agriculture  in 
small  plots,  the  work  be- 
ing done  mostly  by  hand. 
With  heavy  fertilization, 
several  crops  a  year  and 
a  maximum  production 
are  possible.  It  prevails 
in  densely  populated  sub-tropical  countries  where  labor  is  cheap, 
as  in  China,  Japan,  India,  Egypt,  and  some  parts  of  France^ 


Fig.  241.  —  Garden  culture. 


270 


ECONOMIC   GEOGRAPHY 


Spain,  and  Italy.  The  value  of  the  land  is  sometimes  as  high 
as  $1,000  an  acre.  Special  crops,  such  as  celery,  onions,  vegeta- 
bles, small  fruits,  and  flowers  are  grown  by  improved  methods 
of  garden  culture  in  many  parts  of  the  world. 

Agriculture  could  not  reach  its  highest  stage  of  efficiency 
until  animals  were  domesticated  and  trained  for  draft.  Then  a 
heavy,  crotched  stick  could  be  used  as  a  plow,  from  which  the 
many  forms  of  plows  and  cultivators  now  in  use  have  been 
evolved.  Thus  has  arisen  the  prevalent  and,  on  the  whole,  the 
highest  form  of  agriculture,  field  culture,  carried  on  in  fields  and 


Fig.  242.  —  Field  culture. 


farms  of  moderate  size,  largely  by  the  use  of  animal  power.  A 
variety  of  crops  are  grown,  and  domestic  animals  are  bred  for 
food  as  well  as  for  power.  Field  culture  is  general  in  the  tem- 
perate regions  of  North  America  and  Europe,  and  in  smaller 
areas  in  the  other  continents.  Labor  is  relatively  costly.  The 
laborers  are  free,  and  often  independent  owners  of  the  land  they 
cultivate,  with  small  or  moderate  capital. 

In  plantation  culture  (Figs.  245,  248,  260,  261)  special  crops, 
such  as  cotton,  sugar  cane,  coffee,  tea,  and  rubber,  are  grown 


NATURAL  RESOURCES   AND   FOOD   SUPPLY  271 

on  large  tracts.  The  laborers  are  often  of  inferior  native  or 
imported  races,  and  under  some  form  of  servitude;  ownership  and 
control  being  in  the  hands  of  foreign  proprietors  with  large  capital.' 

This  is  the  only  practicable  way,  it  is  said,  of  utilizing  the  labor  supply 
and  developing  the  agricultural  resources  of  tropical  countries.  Natives  of 
such  countries  will  not  work  steadily  even  for  large  wages,  and  are  made  to 
work,  if  at  all,  under  some  sort  of  compulsion.  White  men,  as  a  rule,  can 
not  work  in  tropical  countries;  the  proprietors  find,  therefore,  that  forced 
native  labor,  or  none  at  all,  are  the  only  alternatives. 

Cereal  Grains.  —  The  most  valuable  domesticated  food  plants 
are  the  cereal  grains,  —  wheat,  corn  (maize),  rice,  oats,  rye,  and 
barley,  —  all  of  which  are  species  of  grass,  and  have  been  greatly 
modified  and  improved  over  the  original  wild  forms. 

Wheat  probably  originated  in  the  highlands  of  western  Asia.  It  is  now 
extensively  grown  in  the  temperate  and  cool  temperate  regions  of  North 


Fig.  243.     -  Harvesting  wheat. 

America  and  Europe,  but  is  profitable  on  tropical  plateaus  and  even  on 
tropical  lowlands  as  a  winter  crop.  It  requires  a  cool,  moist  growing  sea- 
son and  a  warm,  dry  ripening  season.  There  are  hundreds  of  varieties, 
each  adapted  to  special  conditions  of  soil  and  climate;  hence  its  range  is 
very  wide,  extending  from  the  tropic  to  the  polar  circle.  The  world's 
wheat  crop  now  exceeds  3,000  million  bushels  annually.  Of  this  more  than 
half  is  raised  in  temperate  Europe,  and  one  fourth  in  temperate  North 


272 


ECONOMIC   GEOGRAPHY 


America.  The  subtropical  countries  of  Europe  and  Asia  produce  about 
one  fifth.  There  was  a  total  increase  of  nearly  one  fifth  in  the  ten  years 
1900-1910,  which  is  approximately  equal  to  the  increase  of  population  in 
wheat-eating  countries.  The  average  yield  per  acre  is  from  eight  bushels 
in  Russia  to  thirty  bushels  in  France,  and  could  be  doubled  by  more  scien- 
tific farming.  The  possible  world's  wheat  crop  of  the  future  is  closely  con- 
nected with  the  available  supply  of  nitrogen  and  phosphorus  (p.  145).  The 
possibilities  of  wheat  growing  in  southern  South  America  are  great,  but 
as  yet  slightly  developed.  The  United  States,  Canada,  Russia,  Roumania, 
Hungary,  India,  and  Argentina  raise  wheat  to  sell,  of  which  Great  Britain 
is  the  largest  purchaser.  The  people  of  France,  United  States,  Great 
Britain,  and  Austria-Hungary  consume  the  most  wheat  per  capita. 

Com.  —  Indian  corn  ^  or  maize  originated  in  the  subtropical  plateaus  of 
America.     It  was  the  only  cereal  known  to  the  American  Indians,  and  is  the 

one  best  fitted  for  primitive 
hoe  culture.  Next  to  rice  it 
is  now  the  largest  of  the 
world's  cereal  crops  and  prob- 
ably the  largest  of  all  food 
crops.  It  requires  a  longer 
and  Warmer  growing  season 
than  wheat,  and  many  days 
of  bright  sunshine  to  ripen  it. 
Hence  its  range  is  from  mid- 
dle temperate  to  sub-tropical 
latitudes,  and  it  is  excluded 
from  oceanic  climates  of  cool 
summers  and  much  cloudi- 
The  world's  crop  is  about  3,800 
million  bushels,  of  which  the  United  States  produces  about  3,000  million 
bushels.  It  is  grown  to  a  limited  extent  in  southern  Europe,  Argentina, 
and  south  Africa.  More  than  half  the  corn  crop  is  fed  to  animals,  chiefly 
swine  and  cattle,  and  thus  converted  into  pork  and  beef.  It  is  also  exten- 
sively used  in  the  manufacture  of  starch,  grape  sugar,  beer,  and  alcohol. 
The  stalks  and  leaves  furnish  excellent  fodder  for  cattle.  The  direct  use 
of  the  grain  for  human  food  is  increasing,  but  in  this  it  still  falls  far  short 
of  wheat. 

^  Corn  is  the  common  name  of  maize  in  the  United  States,  but  in  Great  Britain 
com  is  a  general  name  for  all  grains.  In  England  the  word  usually  means  wheat, 
and  in  Scotland  oats. 


Fig.  244.  —  Com  field. 

ness,  such  as  that  of  the  British  Isles. 


NATURAL  RESOURCES  AND   FOOD   SUPPLY  273 

Oats.  —  The  second  largest  cereal  crop  in  temperate  climates  is  oats, 
nearly  3,600  million  bushels,  of  which  the  United  States  and  Russia  pro- 
duce about  1,000  million  bushels  each,  and  Germany  more  than  half  as 
much.  Oats  thrive  in  a  cooler  and  damper  climate  than  wheat,  and  hence 
have  a  larger  range.  Most  of  the  crop  is  fed  to  horses,  but  it  is  excellent 
for  human  food  and  its  use  is  increasing. 

Rye.  —  Rye  is  a  hardier  grain  than  wheat,  and  can  be  grown  with  profit 
on  soils  where  wheat  cannot.  It  is  used  extensively  by  the  peasants  of 
Russia  and  Germany  as  a  substitute  for  wheat  in  making  "  black  bread," 
and  in  many  countries  in  the  manufacture  of  distilled  liquors.  The  world's 
crop  is  about  1,500  million  bushels,  of  which  Russia  produces  one  half  and 
Germany  one  fourth. 

Barley.  —  Barley  has  a  wider  range  of  latitude  than  any  other  cereal. 
It  was  once  the  chief  breadstuff  of  the  civilized  world,  but  is  now  mostly 
fed  to  stock  and  converted  into  malt  for  brewing  beer.  The  world's  crop 
is  nearly  1,300  million  bushels,  one  fourth  grown  in  Russia  and  the  rest 
well  distributed  throughout  the  grain-producing  countries. 

Rice.  —  The  chief  cereal  grain  of  warm,  wet  climates  is  rice.  It  is  the 
principal  food  crop  of  southeastern  Asia  from  India  to  Japan,  and  the 


Fig.  245.  —  Rice  field. 

breadstuff  of  nearly  one  third  the  human  race.  There  are  several  varieties, 
but  those  extensively  grown  are  water  plants  and  require  flooded  fields  dur- 
ing most  of  the  season.  Hence  alluvial  and  delta  lands  with  abundant 
water  under  control  are  most  favorable.  The  grain  is  not  generally  ground 
to  flour,  but  the  processes  of  hulling  and  polishing  to  remove  chaff  and  skin 


2  74 


ECONOMIC    GEOGRAPHY 


are  complex  and  costly.     With  the  use  of  improved  machinery,  similar  to 
that  used  for  wheat,  the  rice  crop  of  southern  United  States  is  increasing 

rapidly  and  now  amounts  to  21 
million  bushels  a  year.  It  is  impos- 
sible to  ascertain  the  total  world's 
crop,  but  it  probably  exceeds  that 
of  any  other  grain. 

Root  Crops.  —  Root  crops 
are  well  adapted  for  hoe  cul- 
ture, and  are  generally  in- 
dicative of  a  lower  stage  of 
civilization  than  grain  crops. 

In  tropical  countries  the  yam, 
sweet  potato,  manioc  (cassava),  and 
taro  can  be  raised  with  little  labor 
and  furnish  a  large  amount  of  bulky 
food.  The  manioc  of  the  Amazon 
basin  is  the  source  of  tapioca  used 
in  temperate  countries  for  desserts. 
Fig.  246.— Potato  field.  ^^^  |g  ^^^^^  grown  in  the  United 

States  as  food  for  cattle.  The  most  valuable  root  crops  are  potatoes  and 
sugar  beets.  The  potato  originated  in  the  high  plateaus  of  tropical  South 
America,  but  from  its 
common  use  in  Ireland 
has  acquired  the  name 
of  Irish  potato.  The 
world's  crop  is  about 
7,400  million  bushels,  of 
which  Germany  and  Rus- 
sia produce  more  than 
half.  Potatoes  are  used 
in  Europe  as  a  source  of 
starch  and  alcohol. 

Sugar  Beets  are  grown 
chiefly  in  Europe.  Ger- 
many, Austria-Hungary, 


Fig.  247.  —  Sugar  beets. 


Russia,  and  France  produce  four  fifths  of  the  world's  crop.  Seven  milUon 
tons  of  sugar,  or  nearly  half  the  world's  supply,  are  made  from  beets. 
They  are  profitable  in  cool,  dry  climates,  and  supplement  the  tropical 


NATURAL   RESOURCES  AND   FOOD   SUPPLY 


275 


supply  of  sugar  from 
the  cane.  The  pulp 
from  which  most  of  the 
sugar  has  been  extracted 
is  used  to  fatten  swine. 

Sugar    Cane. — 

Sugar  is  not  merely 
a  luxury  and  a  con- 
diment, but  a  valu- 
able and  stimulating 
food.  Its  use  has 
grown  in  a  few  cen- 
turies to  enormous 
proportions.    The  source  of 


Fig.  249.  —  Banana  and  manioc. 


Fig.  248.  —  Cutting  sugar  cane,  Louisiana. 

the  largest  supply  is  the  sugar  cane, 
a  species  of  tropical  grass.  It 
is  grown  from  cuttings  planted 
in  deep,  rich,  moist,  but  well- 
drained  soil,  and  requires  a  hot 
season  of  seven  or  eight  months 
to  mature.  The  canes  are  cut 
and  passed  between  rollers, 
which  press  out  the  juice.  The 
liquid  is  purified  and  evapo- 
rated until  the  sugar  crystal- 
lizes. It  is  afterwards  refined 
to  remove  the  coloring  matter 
and  again  crystallized  into 
white  sugar.  India,  Java,  Cuba, 
United  States,  Hawaii,  and 
Porto  Rico  produce  three 
fourths  of  the  world's  supply. 
Fruits.  —  In  tropical  coun- 
tries fruits  are  the  mainstay 
of  life;  in  temperate  countries 
they  are  in  some  degree  su- 
perfluities and  luxuries.     The 


276 


ECONOMIC   GEOGRAPHY 


quantity  and  variety  of  trop- 
ical fruits  spontaneously  pro- 
duced encourage  collective 
economy  only. 

The  banana  and  its  near  rela- 
tive, the  plantain,  are  the  most 
prolific  of  all  food  plants  and  will 
support  five  times  as  many  people 
per  acre  as  grain.  In  the  East 
Indies  the  rtiango  and  breadfruit, 
and  in  the  oases  and  irrigated 
tracts  of  the  subtropical  deserts 
the  date  palm,  are  in  themselves 
sufficient  to  feed  a  dense  popula- 
tion. In  the  Mediterranean  region 
the  olive  takes  the  place  of  but- 
ter and  meat.  The  citrus  fruits, 
including  many  varieties  of  the 
orange,  lemon,  and  lime,  have 
become  plentiful  in  the  principal 
markets  of  the  world.  The  grape 
has  a  wider  range  than  the  fruits 
above  mentioned,  and  is  common 

both  fresh  and  in  the  form  of  raisins  and  wine.    France  produces  more  wine 

than  any  other  country. 

Of  the  strictly  temperate 

climate  fruits,  apples  are 

the  most  important,  with 

pears,  peaches,  and  plums 

as     a     secondary    crop. 

Cold  storage  and  rapid 

transportation  bring  the 

fruits    of   all    climes    to 

every    civilized   man's 

door,  and  at  almost  all 

seasons.      Fruit    raising 

partakes  of  the  character  ^''^'  251. -Vineyard,  New  York. 

of  both  plucking  and  agriculture,  but  in  the  temperate  zones  it  is  fast 
becoming  a  highly  specialized  branch  of  scientific  agriculture. 


Fig.  250.  — Date  palms. 


J 


NATURAL  RESOURCES   AND   FOOD   SUPPLY 


277 


The  Domestication  of  Animals.  —  The  domestication  of 
animals  was  as  important  a  step  in  human  progress  as  the 
domestication  of  plants.  One  and  perhaps  the  chief  cause  of 
the  backward  condition  of  the  American  Indians  before  their 
contact  with  Europeans  was  the  lack  of  domestic  animals: 
the  only  animals  which  they  domesticated  were  small  species  of 
the  camel  family  in  the  Andes,  and  the  dog.  In  well-populated 
countries  the  dangerous,  destructive,  and  least  useful  animals 
have  been  exterminated,  and  many  of  the  useful  wild  animals 
nearly  so.  Domestic  animals  have  been  bred,  spread,  multiplied, 
diversified,  and  improved  until  they  have  lost  to  a  large  extent 
their  ancestral  characters. 

Herding.  —  In  Eurasia  domestic  animals  have  been  bred 
since  prehistoric  times.     A  lasso  stage,  in  which  wild  animals 


Fig.  252.  —  Herding  in  Asia.     Tents  and  utensils  are  easily  moved. 


are  caught  ahve,  is  intermediate  between  hunting  and  breeding. 
The  vast  steppe  regions  of  central  Eurasia  have  been  for  thou- 
sands of  years  the  home  of  peoples  whose  chief  occupation  is 


278 


ECONOMIC  GEOGRAPHY 


herding.  Their  wealth  consists  of  flocks  and  herds  of  cattle, 
horses,  sheep,  goats,  and  camels,  which  are  driven  from  place 
to  place  in  search  of  fresh  pasturage.  Hence  the  people  are 
nomadic,  having  no  fixed  home,  and  their  houses,  usually  tents, 
and  domestic  utensils  are  all  designed  to  be  easily  movable. 
Political  organization  and  centraHzed  government  are  almost 
impossible,  and  the  place  of  both  is  filled  by  patriarchal  rule,  in 
which  the  head  of  the  family  exercises  control  over  a  group, 
consisting  of  a  family  of  blood  relatives,  with  their  wives,  chil- 
dren, servants,  and  dependents.  The  story  of  Abraham,  Isaac, 
Jacob,  and  Joseph  in  the  book  of  Genesis  gives  a  vivid  picture 
of  nomadic,  patriarchal  life  as  it  was  three  thousand  years  ago, 
and  as  it  still  exists  to-day. 

Cattle.  —  Of  all  the  domestic  animals,  horned  cattle  are  the 
most  important  and  valuable  for  their  flesh,  milk,  and  labor. 

A  damp,  temperate  cH- 
mate,  with  quick-growing 
grass,  is  most  favorable 
for  cattle.  Mountainous 
and  oceanic  lands  pro- 
duce the  best  milk,  steppe 
regions  the  best  meat. 
The  Mediterranean  cli- 
mates, with  dry  summers, 
are  distinctly  unfavora- 
ble. In  some  parts  of 
Africa  cattle  cannot  exist 
on  account  of  a  disease 
communicated  by  the  bite 
of  the  tzetze  fly. 

Cattle  are  numerous  in  all 
the  good  agricultural  countries 
of  the  world,  and  number  about  430  millions.  Europe  has  about  113 
millions,  India  90  millions,  the  United  States  72  millions,  and  Argentina 
30  millions.     In  the  "  Great  Plains  "  or  steppe  region  of  North  America  the 


Fig.  253.  — Herding  cattle,  United  States. 


NATURAL   RESOURCES   AND    FOOD    SUPPLY 


279 


vast  herds  of  wild  bison,  or  buffaloes,  which  once  occupied  them,  have  been 
displaced  by  domestic  cattle  under  the  care  of  "  cowboys."  The  cattle 
thrive  on  the  nutritious  bunch  grass,  which  cures  spontaneously  on  the 
ground,  and  some  live  out  all  winter  by  scraping  away  the  snow  with  their 
hoofs.  When  the  grass  is  covered  with  ice  and  sleet  the  losses  from  cold 
and  starvation  are  very  large.  The  former  free  range  on  public  lands  is 
now  generally  broken  up  and  fenced  into  large  ranches  under  private  own- 
ership, and  the  cattle  are  fed  in  the  winter  with  cut  hay.  The  farmers  of 
the  middle  western  states  buy  large  numbers  of  young  cattle  from  the 
ranches  to  fatten  on  corn  and  fodder.  Kansas  City,  Omaha,  St.  Louis, 
and  Chicago  are  the  principal  cattle  markets  and  slaughtering  and  packing 
centers  of  the  world. 

The  pampas  of  the  Plata  region  of  South  America  furnish  a  vast 
extent  of  pasturage  which  has  never  been  fully  utilized.  Herds  of  cattle 
have  been  bred  there  and  slaughtered  for  their  hides  only,  but  with  cold 
storage  and  improved  means  of  transportation  the  flesh  is  also  marketed. 
South  Africa,  Australia,  and  New  Zealand  are  alr^o  favorable  regions  for 
cattle  raising.  Eastern  United  States  and  Canada,  Ireland,  the  Nether- 
lands, Denmark,  Sweden,  Finland,  France,  and  Switzerland  are  the  leading 
dairy  countries. 

The  zebu  or  humped  cattle  of  India  are  adapted  to  savannas,  and  the 
water  buffalo,  or  carabao  (Fig.  254),  is  the  principal  beast  of  burden  and 
draft  in  China,  Japan,  and  the  PhiUppines,  being  as  well  adapted  for  ser- 
vice in  tropical  swamps  as  the  camel  for  the  desert.  On  the  plateaus  and 
mountains  of  Asia,  above  6,000  feet,  the  yak  is  the  most  hardy  beast  of 
burden,  and  is  used  also  for  milk  and  flesh. 


Sheep. — The  sheep 
is  a  steppe  animal  and 
does  best  in  dry  sub- 
tropical and  temper- 
ate lands  (Fig.  202). 
Sheep  will  live  upon 
short,  scanty  pas- 
turage where  cattle 
would  starve,  and  if 
permitted  will  do  se- 
rious injury  to  graz- 
ing grounds.    Large, 


Fig.  254.  —  Water  buffalo  or  carabao,  Siam. 


28o 


ECONOMIC   GEOGRAPHY 


coarse-wooled  sheep  are  bred  for  mutton,  and  smaller,  fine- 
wooled  animals  for  wool.     In  a  wet  climate  the  wool  is  poor^ 

and  in  a  hot  climate  it  is 
scanty.  Australia,  the  Plata 
countries,  Russia,  and  the 
United  States  lead  in  the 
production  of  wool,  mutton, 
and  hides.  Frozen  mutton 
is  shipped  from  Australia 
and  New  Zealand  to  Europe. 
The  total  number  of  sheep 
in  the  world  is  estimated  at 
more  than  575  millions. 

Goats  are  hardy  animals,  and 

will  pick  up  a  good  living  from 

coarse,  rough  herbage  which  cattle 

and    sheep    would    not    eat.     In 

Fig.  255.  -  Goat.  Switzerland.  mountainous  countries  and  regions 

of  scant  summer  rain,  they  are  bred  for  their  flesh  and  their  milk,  which  is 

very  rich.     Goat  and  kid  skins  are  used  extensively  in  the  manufacture  of 

gloves. 

Horses.  —  The  horse  attains  his  highest  perfection  on  the 
steppes,  where  he  is  admirably  adapted  for  riding,  and  is  used  in 
the  chase,  in  herding,  and  in  war.  Eastern  Europe  and  north 
Africa  have  been  repeatedly  invaded  and  overrun  by  horsemen 
from  the  Asiatic  steppes.  The  horse's  leg  is  a  combination  of 
levers  which  makes  it  mechanically  the  most  efficient  of  animal 
motor  machines.  In  Asia  mares  are  bred  for  their  milk,  which 
forms  the  staple  food  of  many  nomad  peoples.  The  flesh  is 
sometimes  eaten.  The  horse  is  most  used  among  the  most 
advanced  peoples,  and  may  be  regarded  as  the  characteristic 
animal  of  civilization. 

Many  varieties  have  been  developed  for  speed,  beauty,  and  strength 
and  used  for  riding,  driving,  and  draft.  Horse  racing  is  a  favorite  sport 
among  British,  French,  and  American  people.  No  other  animal  is  so  inti- 
mately related  to  human  activities,  and  in  spite  of  the  multiplication  of 
other  means  of  locomotion,  the  horse  is  not  likely  to  lose  his  place  as  the 


NATURAL   RESOURCES   AND    FOOD    SUPPLY 


281 


Fig.  256.  —  Burro. 


most  useful  servant  of  mankind.     The  number  of  horses  in  the  world  is 
about  95  millions. 

The  ass,  or  donkey,  or  burro,  is  less  intelligent  than  the  horse,  but  more 
hardy  and  sure-footed.  He  thrives  on  coarse  fodder,  is  strong  in  proportion 
to  his  size,  and  is  very  useful  as  a 
beast  of  burden  in  rough  countries. 
The  mule,  a  cross  between  the  ass 
and  the  mare,  inherits  the  good 
qualities  of  both  parents,  and  will 
perform  hard  service  in  rough  and 
hot  countries  where  the  horse 
would  fail.  In  1898  it  was  found 
necessary  to  supply  the  British 
army  in  South  Africa  with  mules 
shipped  from  the  United  States 
at  a  cost  of  $1,000  a  head. 

Swine.  —  Pork  has  come 
to  be  second  only  to  beef  in 
the  meat  supply  of  the  world. 
The  hog  is  omnivorous  in  his  diet  and  never-failing  in  appetite. 
He  is  the  only  animal  that,  beginning  at  birth,  can  gain,  on  the 
average,  a  pound  a  day  in  weight  for  250  days.  He  is  the  poor 
man's  animal,  because  he  can  subsist  largely  upon  the  waste 
products  of  the  forest  and  farm.  In  China  swine  are  the  only 
large  domestic  animals,  and  pork  is  the  only  flesh  food  used 
by  the  common  people,  except  birds  and  fish.  More  swine  are 
raised  in  the  United  States  than  in  any  other  country,  and  a 
large  part  of  the  corn  crop  is  converted  into  pork.  There  are 
not  less  than  180  million  swine  in  the  world. 

Camels.  —  The  camel  (Fig.  293)  is  the  domestic  animal  of  the 
warm  deserts,  to  which  he  is  wonderfully  well  adapted.  His  feet 
are  expanded  into  large  pads,  which  prevent  his  sinking  into  the 
sand.  His  stomach  is  triple  and  can  hold  several  gallons  of 
water.  His  nostrils  are  slits  which  can  be  voluntarily  closed 
when  the  air  is  full  of  wind-driven  sand.  His  hump  is  a-  mass 
of  fat,  which  is  absorbed  when  food  is  insufficient.  He  can 
carry  a  load  of  400  to  1,000  pounds,  drink  brackish  water,  and 


282 


ECONOMIC   GEOGRAPHY 


go  a  month  without  drinking.  In  the  deserts  of  Asia  and  north 
Africa  he  is  the  indispensable  beast  of  burden.  In  disposition 
he  is  stupid  and  vicious. 

Four  small  species  of  the  camel  family  are  natives  of  the  Andes  moun- 
tains. The  llama  (Fig.  222)  is  used  in  Peru  and  Bolivia  as  a  beast  of  burden, 
but  will  carry  a  load  of  only  80  pounds.  The  vicuna  and  guanaco  are  raised 
for  flesh  and  wool,  and  the  alpaca  furnishes  a  hair  of  considerable  value  for 
dress  goods. 

Reindeer.  —  The  reindeer  bears  the  same  relation  to  the 
tundra  as  the  camel  to  the  warm  deserts.  Its  foot  is  adapted 
to  snow  as  the  camel's  to  sand.  It  is  bred  in  northern  Eurasia 
for  milk,  flesh,  and  draft.  A  Lapland  family  may  keep  a  herd 
of  500  reindeer.  They  have  recently  been  introduced  into  Alaska 
and  are  found  very  serviceable. 

Dogs.  —  The  dog  was  originally  a  wolf  which  hung  around 
human  habitations  to  steal  food.  He  was  at  first  tolerated  and 
finally  adopted  as  a  domestic  parasite.  He  is  the  only  animal 
except  the  cat  which  man  has  come  to  regard  as  a  member  of 
the  family.  He  has  been  found  useful  as  a  Scavenger,  for  food, 
herding,  hunting,  and  draft;  but  the  large  majority  of  dogs  are 
of  no  use  except  as  pets  and  companions.  In  ice  deserts,  tun- 
dras, and  cold  temperate  for- 


I 


ests  in  winter,  dogs  are  in- 
dispensable draft  animals, 
all  travel  and  transportation 
being  by  dog  sledge.  The 
Arctic  or  Eskimo  dog  is  but 
little  better  than  a  wolf  in 
disposition,  but  he  is  strong 
and  hardy,  can  live  on  frozen 
fish,  and  can  sleep  out  of 
doors  in  any  weather. 

Elephants.  —  The  elephant 

is  kept  in   domestication  in 

India  and  Siam  and  used  for  riding,  hunting,  and  display.     His 

strength  and  intelligence  render  him  valuable  in  more  menial 


mm 


Fig.  257.  —  Elephant. 


NATURAL  RESOURCES  AND   FOOD   SUPPLY 


283 


Fig.  258.  —  Poultry. 


employments,  such  as  haul- 
ing and  piling  timber.  The 
wild  African  elephant  has 
been  hunted  for  pleasure  and 
for  his  tusks,  which  furnish 
ivory,  until  the  species  is 
threatened  with  extinction. 

Poultry.  —  The  domestic 
birds  include  the  common 
fowl,  goose,  duck,  pigeon, 
turkey,  guinea  fowl,  peafowl, 
and  ostrich.  The  common 
barnyard  fowl,  descended  from  the  wild  jungle  cock  of  India,  is 
one  of  the  most  valuable  of  animals.  Many  varieties  have  been 
•developed  by  breeding  and  have  spread  to  nearly  all  parts  of 
the  habitable  world.  The  flesh  and  eggs  are  so  palatable  and 
nutritious  as  to  be  generally  esteemed  as  semi-luxuries.  The 
total  value  of  poultry  and  eggs  produced  in  the  United  States 
annually  is  about  $400,000,000. 

Geese  and  ducks  are  waterfowl  bred  for  flesh,  eggs,  and  feathers.  Do- 
mestic pigeons  are  largely  "  fancy  "  birds,  bred  to  many  fantastic  forms 
and  used  to  a  limited  extent  as  food.  The  turkey,  the  only  domestic  bird 
native  to  America,  is  scarcely  known  elsewhere.  The  guinea  fowl  from 
Africa  and  the  peafowl  from  Asia  are  more  ornamental  than  useful.  The 
African  ostrich  (Fig.  221)  is  valuable  for  his  plumes. 

Insects.  —  The  only  domesticated  insects  are  the  silkworm 
and  the  bee. 

The  breeding  and  care  of  the  honey  bee  has  become  a  highly 
specialized  art  in  nearly  all  civiHzed  countries.  The  honey  is 
made  by  the  bees  from  the  nectar  of  flowers  and  stored  in  combs 
or  cells  of  wax  for  their  own  use  and  for  feeding  the  young. 
With  proper  management  a  swarm  of  bees  will  produce  a  large 
surplus  beyond  their  own  needs. 

The  silkworm  is  the  caterpillar  of  a  moth  which  spins  a  cocoon 
yielding  the  fiber  of  raw  silk.  The  caterpillars  are  hatched  and  fed 
upon  the  leaves  of  mulberry  trees  which  are  grown  for  the  purpose. 


284 


ECONOMIC   GEOGRAPHY 


China,  Japan,  Italy,  and 
France  furnish  nearly  all  the 
raw  silk  that  is  produced. 

Physiological  Luxuries  and 
Medicines.  —  There  is  a  large 
class  of  substances,  mostly 
of  vegetable  origin,  which 
have  Httle  or  no  value  as 
food,  but  which  men  use  in- 
ternally for  various  purposes. 
They  include  spices,  condi- 
ments, and  flavors  which  give 
food  an  agreeable  taste  or 
stimulate  digestion,  stimu- 
lants and  narcotics  which 
produce  agreeable  sensations, 
and  medicines  which  relieve 
pain  or  assist  in  the  cure  of 
disease. 

Condiments  and  Spices.  —  In  the  Middle  Ages,  spices  were 
among  the  most  valuable  goods  which  could  be  marketed  in 
Europe,  because  they  rendered  dried  and  salted  meats  and 
poorly  cooked  food  more  palatable.  Arabia  was  called  "  the 
land  of  spices  "  because  the  supply  came  through  that  country 
from  the  Far  East.  The  blockade  of  the  caravan  routes  by  the 
Turks  stimulated  efforts  to  open  a  sea  route  to  the  ^'  spice 
islands  "  and  led  directly  to  the  voyages  of  Da  Gama  around 
Africa  and  of  Columbus  to  America. 


Fig.  259.  —  Feeding  silkworms. 
The  silkworms  are  the  white  objects  in  the  trays. 


Mustard  is  now  the  most  important  condiment  and  the  most  widely  dis- 
tributed. It  is  made  from  the  seed  of  several  plants  grown  in  Europe,  the 
United  States,  Asia,  and  the  East  Indies.  Vinegar,  made  from  cider,  wine, 
and  other  alcoholic  liquors,  is  in  common  use  in  all  civilized  countries. 

Spices  are  tropical  products  grown  in  India,  Ceylon,  China,  the  East 
and  West  Indies,  Zanzibar,  Mexico,  and  South  America.  Pepper  is  made 
from  dried  berries,  cloves  from  flower  buds,  nutmegs  from  fruit  stones, 


NATURAL  RESOURCES   AND   FOOD   SUPPLY 


285 


cinnamon  from  bark,  and  ginger  from  roots.     Cayenne  or  red  pepper  and 
vanilla  are  the  fruits  of  plants  grown  chiefly  in  Mexico. 

Stimulants  and  Narcotics.  —  Alcoholic  liquors  are  used  by 
people  of  nearly  all  races,  countries,  and  classes.  Their  use  is 
prohibited  among  the  behevers  of  the  Mohammedan  religion. 
They  are  made  by  the  fermentation  of  sugar  derived  from  fruits, 
grains,  roots,  or  any  material  containing  starch.  The  yeast 
plant,  a  microscopic  organism,  is  the  only  agent  known  by 
which  sugar  can  be  converted  into  alcohol  cheaply  and  on  a 
large  scale.  The  yeast  is  added  to  a  solution  containing  sugar 
or  allowed  to  grow  from  spores  everywhere  present  in  the  air. 

Wines  of  many  varieties  are  made  from  the  fermentation  of  grape  juice, 
and  are  the  common  beverage  in  the  warm  temperate  regions  of  Europe. 
Beer  is  made  from  barley  or  corn  and  is  a  favorite  drink  in  northern 
Europe.  Distilled  liquors  contain  a  much  higher  percentage  of  alcohol 
than  wine  or  beer.  Whisky  is  distilled  from  corn,  rye,  and  potatoes, 
brandy  from  wine,  and  rum  from  sugar  cane.  In  Japan  sake  is  made  from 
rice,  in  Mexico  pulque  from 
the  century  plant,  and  in 
India  toddy  from  the  coco- 
nut palm.  From  any  of  these 
sources  pure  alcohol  may  be 
obtained  by  careful  distilla- 
tion, and  is  manufactured  in 
large  quantities,  not  for  drink- 
ing, but  as  a  chemical  product 
used  in  many  important  arts 
and  for  fuel.  Alcohol  has  no 
direct  food  value,  but  is  a 
stimulant  and  intoxicant,  more 
or  less  injurious  to  body  and 
mind. 

Coffee,    tea,    mate,   and 
cocoa  are  mild  stimulants, 
not  intoxicating,  and  gen- 
erally harmless.    Coffee  is  the  seed  of  a  small  tree  grown  by  the 
plantation  system  chiefly  in  Brazil,  and  in  smaller  quantities  in 
Venezuela,  Central  America,  Java,  Mexico,  and  the  West  Indies. 


Fig.  260.  —  Coffee  plantation,  Straits  Settlements. 


286 


ECONOMIC   GEOGRAPHY 


Fig.  261.  —  Picking  tea. 


The  total  crop  is  about  2,400  million  pounds,  of  which  Brazil  fur- 
nishes three  fourths.    It  is  used  more  largely  in  the  United  States 

than  in  any  other  country. 

Tea  is  the  dried  young  leaves 
of  a  shrub  which  yields  best  on 
tropical  highlands  with  warm, 
rainy  summers.  China  and 
Japan  have  had  until  recently 
a  monopoly  of  tea  growing, 
but  now  the  plantations  of 
India  and  Ceylon  furnish  three 
fifths  of  the  680  milKon  pounds 
exported.  Russia  and  Great 
Britain  are  the  largest  con- 
sumers of  tea.  Yerha  mate,  or 
Paraguay  tea,  consists  of  the 
dried  leaves  of  a  tree  growing 
wild  in  southern  South  America  and  possesses  the  same  stimula- 
ting qualities  as  tea.    Its  use  is  local,  very  little  being  exported. 

Cocoa  and  chocolate  are  pre- 
pared from  cacao  beans,  the 
seeds  of  a  tree  which  grows 
in  the  lowlands  of  tropical 
America,  the  East  Indies,  and 
west  Africa.  They  contain  a 
mild  stimulant  and  a  large 
percentage  of  oil,  starch,  and 
albuminoids  which  render  them 
highly  nutritious. 

Tobacco  and  opium  are  nar- 
cotic  stimulants  possessing 
decided  physiological  and  me- 
dicinal properties.  Tobacco, 
originally  a  native  of  America, 
has  in  the  last  300  years  ex-  Fig.  263.  —  cacao  tree, 


NATURAL  RESOURCES  AND   FOOD   SUPPLY 


287 


Fig.  263.  —  Tobacco  field. 


tended  over  the  entire  world,  and  has  come  into  general  use 
among  all  kinds  of  people.  Naturally  a  semi-tropical  plant,  it 
is  now  grown  as  far  north  as  Connecticut,  Wisconsin,  and  Ger- 
many. Its  quality,  flavor, 
and  value  are  greatly  modi- 
fied by  soil,  climate,  cultiva- 
tion, and  curing.  It  requires 
a  growing  season  at  least  as 
long  as  corn,  but  is  much 
more  exhausting  to  the  soil. 

The  whole  plant  is  cut  and  hung 
up  to  dry,  the  leaves  are  stripped 
off  and  slightly  "  sweated  "  or  fer- 
mented, the  stems  are  removed 
and  the  blades  rolled  into  cigars 
or  put  up  in  various  forms  for 
smoking  and  chewing.  The  "  seed 
leaf"  used  for  cigar  wrappers  is 
grown  in  Sumatra,  the  Philippines, 
and  the  Connecticut  valley,  where  the  gross  value  of  the  crop  is  sometimes 
$10,000  an  acre.  The  relation  of  tobacco  to  the  human  race  is  unique. 
Purely  a  luxury,  and  with  no  beneficial  effect  upon  the  system,  it  is  a  mild 
narcotic  which,  though  usually  injurious,  is  not  ruinous,  and  has  an  attrac- 
tion for  people  of  all  classes,  from  the  most  degraded  to  the  most  refined, 
possessed  by  no  other  substance  except,  perhaps,  alcohol.  The  United 
States  and  India  produce  more  than  half  the  crop  of  2,200  million  pounds. 

Opium  is  the  dried  juice  of  the  white  poppy  grown  in  India, 
China,  Persia,  and  Turkey.  It  is  smoked  in  small  pipes  as  a 
narcotic  by  the  Chinese  and  other  Oriental  peoples.  Its  effects 
are  much  more  serious  than  those  of  tobacco,  and  opium  smok- 
ing in  China  has  become  a  national  danger.  Morphine,  lauda- 
num, and  other  derivatives  of  opium  are  extensively  used  in 
medicine  to  reheve  pain,  but  should  never  be  taken  except 
under  the  direction  of  a  physician,  since  there  is  grave  danger  of 
acquiring  the  opium  habit,  which  is  very  difficult  to  cure. 

Medicines.  —  Medicines  are  largely  extracted  from  crude 
drugs,  or  the  dried  bark,  leaves,  and  seeds  of  plants.     The  vari- 


28S  ECONOMIC   GEOGRAPHY 

eties  in  common  use  are  very  numerous,  and  most  of  them  are 
of  great  value  for  the  relief  and  cure  of  disease.  Of  substances 
which  are  purely  medicinal,  wholly  beneficial,  and  almost  in- 
valuable to  man,  quinine  may  be  taken  as  a  type.  It  is  obtained 
from  the  bark  of  the  cinchona  tree,  a  native  of  the  tropical 
South  American  forest.  The  natural  supply  has  long  been 
insufficient,  and  the  cinchona  plantations  of  Java  now  furnish 
86  per  cent  of  the  17  million  pounds  of  bark  required  to  supply 
the  world.  Quinine  is  the  only  safe  and  efficient  antidote  to 
malaria,  and  without  it  the  occupation  of  the  tropics  by  white 
men  would  have  been  impossible. 


CHAPTER   XX 

CLOTHING   AND    CONSTRUCTIVE   MATERIALS 

Clothing.  —  After  food,  the  object  for  which  the  greatest 
amount  of  human  energy  is  expended  is  clothing.  Clothes  are 
not  naturally  as  important  as  they  seem.  They  are  not  required 
and  are  not  worn  for  protection  by  half  the  people  in  the  world. 
The  natives  of  Tierra  del  Fuego  in  55°  S.  Lat.  go  naked  and  do 
not  appear  to  suffer.  In  tropical  regions  the  common  people 
wear  very  little  clothing,  and  that  chiefly  for  ornament.  Civil- 
ized people  are  prevented  from  going  naked  by  a  sense  of 
modesty,  and  a  sense  of  what  is  becoming  or  in  fashion  deter- 
mines the  material,  cut,  style,  color,  and  other  details.  The 
simplest  of  all  dress  is  the  coat  of  clay  and  mineral  paint  used 
by  the  Australian  black  fellow,  or  the  mixture  of  grease  and 
soot  with  which  a  Central  African  belle  anoints  herself.  They 
are  regarded  as  ornamental,  and  they  furnish  some  protection 
against  insects.  Some  articles  of  clothing  have  come  into  use 
for  convenience  in  carrying  small  articles,  as  the  belt  around  the 
waist,  and  bands  around  the  arms.  Simple  clothing  is  often 
made  of  leaves,  bark,  grass,  or  straw,  more  or  less  skillfully 
braided  or  woven  together.  In  regions  of  cold  winters,  men 
rob  animals  of  their  fur,  feathers,  and  skins. 

All  these  things  are  obtainable  by  collective  economy,  but  herding  and 
agriculture  are  necessary  to  supply  light,  pliable,  comfortable,  and  durable 
garments,  which  are  generally  woven  from  some  kind  of  fiber,  and  arc 
therefore  called  textiles.  The  principal  vegetable  fibers  are  cotton  and 
linen,  and  the  principal  animal  fibers  are  wool  and  silk. 

Cotton.  —  The  hairs  which  cover  the  seeds  and  fill  the  bolls 
of  the  cotton  plant  furnish  the  best  fiber  known  for  cloth  and 
small  cordage.     It  is  strong,  soft,  fine,  flexible,  and  easily  dyed 

28a 


290 


ECONOMIC    GEOGRAPHY 


and  washed,  —  an  almost  ideal  combination  of  qualities.  Cotton 
produces  the  best  fiber  in  a  tropical  climate  near  salt  water. 
It  is  grown  from  seed,  cultivated  like  corn,  and  picked  usually 


m..,^^ 

1^ 

,,^a4  ,.vaHisftMs 

^M 

W^^^ 

N^ 

^  '^W^^^i 

mm 

t  a  ■»  • 

%  ;^         »    *^^  ^    ^ 

•  'M% 

*f^a   r   ♦•      .j 

Fig.  264.  —  Cotton  field,  South  Carolina. 

by  hand.  The  seeds  are  separated  from  the  fiber  by  a  machine 
called  a  gin,  and  contain  an  oil  valuable  for  food  and  for  soap 
making. 

On  account  of  the  large  amount  of  hand  labor  required,  cotton  has  gen- 
erally been  grown  by  the  plantation  system.  The  invention  of  the  gin,  the 
spinning  jenny,  and  the  power  loom,  in  the  latter  part  of  the  eighteenth 
century,  made  it  possible  to  utilize  large  quantities  of  the  fiber,  which  stimu- 
lated production  and  increased  the  supply  until  cotton  became  the  cheapest 
and  most  plentiful  of  all  textiles.  The  invention  of  a  successful  machine 
for  picking  cotton  will  put  cotton  cloth  practically  within  reach  of  every 
human  being.  The  world's  cotton  crop  is  about  10,000  million  pounds,  of 
which  the  United  States  produces  two  thirds,  India  one  seventh,  and  Egypt 
one  twelfth. 

Linen.  —  Linen  is  made  from  the  fiber  of  the  stem  of  the 
flax  plant.  The  process  of  separating  it  from  the  wood  and 
preparing  it  for  spinning  is  long  and  difficult.  Hence  linen  is 
far  more  expensive  than  cotton,  and  is  used  for  laces,  napkins. 


CLOTHING   AND   CONSTRUCTIVE  MATERIALS 


291 


and  articles  of  luxury.  Flaxseed  furnishes  linseed  oil,  which  is 
indispensable  in  mixing  good  paint.  Russia  produces  about 
four  fifths  of  the  world's  supply  of  flax. 

Wool.  —  The  animal  fibers  most  useful  for  cloth  are  obtained 
from  sheep,  goats,  and  camels,  including  the  alpaca  and  vicufia. 
Sheep's  wool  is  used  in  all  cold  countries  for  heavy  clothing, 
especially  that  worn  by  men.  Australia,  Argentina,  and  Russia 
produce  about  half  the  wool  supply. 

Silk.  —  The  silkworm  spins  a  cocoon  of  fine,  lustrous,  elastic 
threads  which  form  the  raw  silk  of  commerce.  A  large  amount 
of  hand  labor  is  required  in  feeding  and  caring  for  the  worms, 
unwinding  the  threads,  and  pre- 
paring them  for  the  loom,  hence 
the  industry  is  confined  to  coun- 
tries where  wages  are  low. 

Artificial  silk,  but  little  inferior  to 
the  natural  fiber  and  much  cheaper,  is 
now  being  manufactured.  For  service- 
able clothing  silk  is  inferior  to  cotton 
and  wool,  but  is  superior  in  beauty. 
It  is  used  extensively  for  laces,  rib- 
bons, and  velvets. 

Rubber.  —  The  milky  sap  of 
various  species  of  tropical  plants 
forms  a  gummy  mass  when  dried, 
and  is  used  to  render  textiles 
waterproof.  Most  of  the  sup- 
ply is  obtained  from  native  wild 
plants  of  Brazil  and  central  Af- 
rica, but  rubber  plantations  are 
increasing  in  number  and  im- 
portance. 

Furs  and  Leather.  —  The  skins 
of  animals  have  always  formed 
an  important  part  of  human  clothing,  either  cured  with  the  fur 
on  or  converted  into  leather.     Deerskin  was  the  chief  reliance 


Fig.  265.  —  Rubber  trees. 

The  marks  on  the  trees  are  cuts  in  the 

bark,  from  which  to  collect  the  sap. 


292 


ECONOMIC   GEOGRAPHY 


Fig.  266.  —  Straw  hut,  Hawaii. 


of  the  North  American  Indian,  as  sealskin  is  of  the  Eskimo,  and 
sheepskin  of  the  shepherd  peoples  of  Eurasia. 

Among  highly  civilized  peoples  furs  have  become  articles  of  luxury, 
and  some,  such  as  seal,  otter,  ermine,  marten,  sable,  beaver,  and  silver  fox, 
command  fabulous  prices.  Canada  and  Russia  are  the  principal  fur-pro- 
ducing countries.  Leather,  made  by  soaking  hides  in  a  solution  of  tan- 
bark  or  other  chemical  agent  which  renders  them  tough  and  impervious 

to  water,  has  become  an  indispen- 
sable article  for  shoes  and  gloves. 
Thus  men  protect  their  extremities 
which  are  most  exposed  to  rough 
usage.  Leather  is  made  from  the 
skins  of  cattle,  horses,  swine,  sheep, 
goats,  dogs,  and  many  other  an- 
imals. 

Shelter.  —  Few,  if  any,  hu- 
man beings  live  so  simply  as 
never  to  need  shelter  of  any 
kind.  Some  kind  of  a  lair  is 
necessary  as  a  place  for  rest  and  sleep.  A  tree,  forest,  over- 
hanging rock,  or  cave  may  furnish  shelter  from  heat,  cold,  wild 
animals,  or  enemies,  and  men 
soon  learn  to  improve  these 
natural  advantages.  Sticks, 
grass,  leaves,  and  boughs  are 
among  the  most  easily  availa- 
ble materials,  and  a  large  part 
of  the  human  race  still  live 
in  more  or  less  elaborate  huts 
made  from  them.  With  the 
progress  of  the  mechanic  arts 
men  have  become  able  to  use 
trees  for  timber  and  to  con- 
struct from  them  commodious 
and  luxurious  homes.     Hence  Fig.  267.— Log  house, 

have  arisen  all  the  refinements  of  lumbering,  carpentry,  and 
cabinet  work. 


CLOTHING  AND   CONSTRUCTIVE   MATERIALS 


293 


Among  the  early  inhabitants  of  Europe  were  the  cave  men,  who  inhabited 
the  natural  limestone  caverns,  furnished  them  with  the  skins  of  wild  beasts, 

and  even  decorated  their  walls  with 

paintings.  In  some  parts  of  France 
inhabited  houses  and  even  churches 
are  still  made  by  enlarging  and  im- 
proving natural  caverns.  In  China 
thousands  of  people  live  in  houses 
dug  out  of  the  soft  but  firm  deposits 
of  loess  (p.  144),  and  the  pioneer 
in  the  American  prairies  and  steppes 
often  lives  at  first  in  a  "  dugout " 


Fig.  268.  —  Rock  house,  France. 

or  in  a  sod  house.     The  Eskimo 
finds  chunks  of  frozen  snow  cut  to 

Fig.  a69.-Sod  house.     (U.S.G.S.)  P^^P^^  ^^^P^  ^^^  ^^^^  ^^^^^^^^  ^^^ 

building  a  hut  adapted  to  his  needs 
in  an  Arctic  climate.  In  countries  of  small  rainfall  and  with  alluvial  or 
adobe  soils,  sun-dried  bricks  are 
easily  made  and  built  into  huts  or 
houses  which  are  comfortable  and 
permanent. 

In  most  parts  of  the  world 
clay  is  plentiful,  from  which 
bricks  can  be  made  and  hard- 
ened by  burning  into  excel- 
lent building  materials .  Many 

kinds    of    rock,    such    as    sand-     Copyright  ly  Doubleday,  Page  &  Co. 

stone,  limestone,  granite,  and       ^'^-  ^^°--i«^-°  -  e^^°^°  --'^  ^°-- 
slate,  are  quarried  and  used  to  construct  the  most  substantial 


294 


ECONOMIC   GEOGRAPHY 


and  imposing  buildings.  For  many  thousand  years  various  ores, 
especially  those  of  iron,  have  been  mined  and  smelted  and  the 
extracted  metals  used  in  all  sorts  of  construction.  Hence  the 
industries  of  quarrying,  mining,  and  metallurgy  have  grown  to 

enormous  proportions.  These 
industries  belong  to  scientific 
collective  economy,  since  they 
collect  and  utilize  natural 
materials,  but  do  not  produce 
them  as  in  agriculture  or 
stock  raising. 

Timber.  —  Of  all  materials 
for  construction  wood  is  the 
most  generally  useful,  and  for 
most  purposes  that  furnished 
by  the  coniferous  forests  (pp. 
234-236)  is  the  best. 

Pine,  spruce,  fir,  hemlock,  larch, 
cedar,  and  redwood  lumber  is  light, 
strong,  durable,  and  easily  worked, 
and  can  be  had  in  pieces  of  large 
dimensions.  None  is  better  than 
the  white  pine  of  North  America, 
which  is  ten  times  as  strong  as 
steel  of  equal  weight.  The  yellow 
or  hard  pine  of  the  southern  States 
is  full  of  resin,  from  which  turpen- 
tine, rosin,  and  tar  are  extracted. 
The  timber  is  hard,  strong,  dura- 
ble, and  fit  for  heavy  construction, 
while  its  beautiful  color  and  grain 
make  it  desirable  for  inside  work 
in  houses.  The  Douglas  fir  of  the 
Pacific  coast  of  North  America  is  especially  valuable  in  ship-building  on 
account  of  the  length  and  size  of  timbers  which  can  be  cut  from  it.  Cali- 
fornia redwood,  a  near  relative  of  the  Sequoias,  or  "  big  trees,"  is  famous 
for  the  size  of  the  individual  trees  and  the  yield  of  merchantable  lumber 
per  acre.    Redwoods  grow  from  200  to  300  feet  high,  with  a  diameter  of 


Fig.  271.  —  Redwoods,  Oregon. 

200  to  300  feet  high.  * 


CLOTHING   AND    CONSTRUCTIVE   MATERIALS  295 

10  to  20  feet,  and  so  close  together  that  it  is  difficult  to  drive  a  wagon 
between  them.  The  redwood  forests  are  confined  to  the  Coast  Ranges 
of  California  and  Oregon,  and  at  the  present  rate  of  cutting  are  likely  to 
disappear  at  an  early  date.  White  spruce  is  being  cut  at  a  rapid  rate 
for  the  manufacture  of  paper  pulp.  White  cedars  are  used  largely  for 
posts,  telegraph  poles,  and  shingles;  and  red  cedar,  or  juniper,  is  famihar 
in  lead  pencils.  These  cedars  are  well  distributed  throughout  the  forest 
regions  of  the  United  States  and  Canada.  The  hemlock  of  the  north  and 
the  cypress  of  the  south  are  inferior  to  the  pine  as  timber  trees,  but  are 
used  as  a  substitute  for  it.  The  Norway  spruce,  the  European  pine,  fir, 
and  larch,  and  the  Indian  cypress  and  deodar  are  among  the  chief  timber 
trees  of  their  respective  countries.  The  area  of  coniferous  forests  in  north- 
ern North  America  and  Eurasia  is  very  large  (Fig.  192).  No  part  of  it  is 
more  valuable  than  that  on  the  Pacific  coast  from  California  to  Alaska. 

The  broad-leaved  and  generally  deciduous  timber  trees  are 
more  widely  distributed  and  of  greater  variety  than  the  con- 
iferous trees. 

The  tulip  tree,  poplar,  and  linden,  or  basswood,  common  in  eastern 
United  States,  furnish  soft,  light  wood  easily  worked.     The  linden  is  com- 


-  •''  fi'  Fjg.  272.  —  Floating  logs  to  a  sawmill.     (U.S.G.S.) 

mon  in  Europe.  Of  close-grained  hardwoods  the  maple,  beech,  birch,  and 
sycamore,  or  plane  tree,  exist  in  many  species  throughout  temperate  North 
America  and  Europe.  Among  the  coarse-grained  hardwoods  the  oaks  hold 
the  first  place  in  number  of  species,  wide  distribution,  and  value  of  timber. 


296 


ECONOMIC   GEOGRAPHY 


They  are  the  most  abundant  timber  trees  of  eastern  North  America  and 
Europe,  and  extend  across  south  central  Asia  to  Japan.  Cork  is  the  bark 
of  a  species  of  oak  growing  in  the  Mediterranean  region.  The  ash,  chest- 
nut, elm,  hickory,  locust,  and 
many  other  less  important 
trees  furnish  wood  of  much 
value  for  various  purposes. 
Among  the  woods  famous  for 
their  beauty  of  color  and 
grain,  and  commanding  high 
prices  for  furniture,  cabinet 
work,  and  interior  finish,  the 
black  walnut,  butternut, 
cherry,  and  gum  are  native 
to  eastern  United  States. 
Still  more  highly  prized  is 
mahogany,  imported  from 
tropical  America  and  west 
Africa  to  Europe  and  the 
United  States.  Rosewood  and 
ebony  are  tropical  woods  used 
One  of  the  most  valuable  of 


p — =- 

t 

^     <' 

\ 

,- ^^i 

Fig.  273.  — Sawmill,  North  Carolina.     (U.S.G.S.) 


entirely  for  fancy  or  ornamental  purposes. 

all  woods  for  heavy  construction  is  the  teak  of  India,  Indo-China,  and  the 

East  Indies.     The  gum 

or    eucalyptus    trees    of 

Australia  are  not  much 

inferior  to  teak. 

Lumbering. — 

Lumbering  is  a  form 
of  specialized  collec- 
tive economy,  which 
consists  in  cutting 
trees  into  logs  and 
transporting  them  by 
sled,  wagon,  rail,  or 

water   to   mills    to   be  Fig- 274-  —  Burned  forest,  Washington.     (U.S.G.S.) 

sawed,  planed,  and  otherwise  elaborated  for  particular  uses. 

The  people  of  Europe  and  the  United  States  have  destroyed  their  native 

forests  to  such  an  extent  that  timber  has  become  scarce  and  high-priced. 


CLOTHING  AND   CONSTRUCTIVE   MATERIALS 


297 


The  future  supply  must  be  largely  imported  from  the  northern  forests,  or 
much  of  the  land  originally  timbered  must  be  reforested.  The  conserva- 
tion of  forests,  which  includes  the  cutting  of  timber  without  unnecessary 
waste,  the  prevention  of  forest  fires,  and  the  replanting  of  tracts  of  little 
value  for  other  purposes,  is  one  of  the  most  important  problems  of  present- 
day  economics.  The  science  of  forestry  has  been  highly  developed  in  Ger- 
many and  is  being  taken  up  in  the  United  States. 


Fig.  275.  —  Result  of  deforestation,  China.    The  land  has  been  ruined  by  erosion. 

Paper.  —  Paper  is  made  from  various  vegetable  fibers  by 
grinding  and  digesting  to  a  pulp,  which  is  then  rolled  into  sheets. 
Fine  book  and  writing  papers  are  made  from  Knen,  coarse 
wrapping  paper  from  straw,  and  newspaper  from  wood  pulp. 
The  spruce  forests  of  North  America  are  being  rapidly  used  up 
in  the  manufacture  of  wood  pulp. 

Clay.  —  Of  all  minerals  used  in  construction,  clay  is  the  most 
widely  diffused  and  readily  available.  It  is  a  product  of  the 
decay  of  feldspar.     By  mixing,  molding,  and  heating,  common 


298 


ECONOMIC   GEOGRAPIIY 


Fig.  276.  —  Clay  works. 


clay  is  made  into  building, 
paving,  and  fire  brick,  tiling, 
sewer  pipe,  and  pottery.  Pure 
clay,  or  kaolin,  is  mixed  with 
other  materials  to  make  fine 
porcelain  and  chinaware. 

Cement.  —  Mortar  made 
of  quickhme  and  sand  is  gen- 
erally used  to  bind  brick  and 
stone  work  together.  In  re- 
cent years,  owing  partly  to 
the  increasing  cost  of  wood, 
hydraulic  or  Portland  cement, 
made  by  heating  and  grind- 
ing a  mixture  of  clay  and 
lime,  has  come  into  gen- 
eral use.  The  mixture  of  cement,  sand,  and  gravel  or  broken 
stone  called  concrete  is  really  an  artificial  conglomerate,  and 
is  displacing  brick  and 
other  materials  in  pav- 
ing and  house  building. 
When  reinforced  by  an 
imbedded  framework  of 
steel,  concrete  is  superior 
to  steel  or  stone  alone 
for  bridge  construction. 
Building  Stone.  — 
Stone  is  used  the  world 
over  for  foundations, 
bridge  piers,  docks,  break- 
waters, pavements,  pub- 
lic buildings,  and  costly 
private    structures.      Its 

value  depends  upon  many         ^'^-  ^^^^ "  Quarrying  granite,  New  Hampshire. 

factors,  such  as  ease  of  quarrying  and  working,  strength  under 
a  crushing  load,  hardness,  color,  and  resistance  to  weather. 


I 


CLOTHING   AND    CONSTRUCTIVE   MATERIALS 


299 


Probably  limestone  is  most  extensively  used,  but  sandstone,  granite, 
and  volcanic  rocks  of  various  kinds  are  valuable.  Metamorphic  limestone, 
or  marble,  on  account  of  its  beautiful  colors  and  the  high  polish  of  which 
it  is  capable,  is  a  favorite  ornamental  stone  for  buildings,  monuments, 
statuary,  and  furniture. 

Quartz,  the  most  abundant  of  all  solid  minerals,  occurs  in 
massive  quartzite  and  sandstone,  in  common  sand,  and  in  trans- 
parent crystals.     It  has  many  colors. 

Agate,  amethyst,  onyx,  chalcedony,  carnelian,  chrysoprase,  heliotrope, 
jasper,  opal,  and  many  other  varieties  of  quartz  are  semi-precious  stones 
prized  for  their  color  and  luster.  Millstones,  grindstones,  and  whetstones 
are  fine-grained  sandstones.  Flint  is  a  hard  variety  of  quartz  which  was 
used  all  over  the  world  before  the  discovery  of  iron  for  weapons  and  cutting 
implements.  Glass  is  made  by  heating  a  mixture  of  pure  quartz  sand  and 
soda  ash  to  a  very  high  temperature.  Most  glass  articles  are  shaped  by 
blowing  air  into  melted  glass  through  a  metal  tube.  Various  ingredients 
are  added  to  give  color,  luster,  and  other  special  qualities. 

Ores  and  Metals.  —  An  ore  is  a  mineral  from  which  a  metal 
may  be  profitably  extracted.  Most  ores  have  been  deposited 
by  solution  in  ground  water 
which  rises  from  the  depths 
of  the  earth,  and  occur  in  fis- 
sures called  veins,  lodes,  and 
leads;  consequently  valuable 
deposits  of  ore  are  found 
chiefly  in  mountainous  re- 
gions, where  the  earth  crust 
has  been  broken,  and  in  old, 
worn-down  plains  (pp.  44,  53, 
58)  from  which  a  great  thick- 
ness of  the  crust  has  been  re- 
moved by  erosion. 

Iron.  —  Of  all  the  metals, 

,  -    ,  Fig.  278.  —  Iron  mine,  Minnesota. 

iron   is   the   most    useful    to 

mankind.    No  people  have  ever  been  able  to  attain  a  high  state 

of  civilization  without  the  use  of  iron.     It  is  the  physical  basis 


300 


ECONOMIC   GEOGRAPHY 


of  modern  industry.  Its  extraction  from  the  ore  is  difficult 
and  requires  such  a  high  temperature  that  the  progress  of  the 
human  race  was  delayed  thousands  of  years  for  lack  of  it. 

As  long  as  all  implements  and  tools  were  made  of  wood,  with  points 
and  cutting  edges  of  stone,  no  great  material  civilization  was  possible. 
Iron  is  supreme  because  it  is  abundant,  strong,  and  workable.  When  hot 
it  can  be  hammered  into  shape,  when  melted  it  can  be  cast  in  molds,  and  in 
the  form  of  steel  it  can  be  given  a  high  degree  of  hardness  and  elasticity. 
If  kept  dry  it  is  very  durable,  but  if  damp  it  rapidly  rusts. 

Iron  ores  are  smelted  with  charcoal  or  coke,  and  limestone  to  absorb 
impurities,  in  a  furnace  which  is  raised  by  a  blast  of  hot  air  to  a  tempera- 


Fig.  279.  —  Blast  furnaces,  Gary,  Ind. 

ture  of  nearly  3,000  degrees.  The  liquid  metal  drawn  from  the  furnace  is 
pig  or  cast  iron,  which  is  moderately  hard  and  relatively  brittle,  but  can 
be  cast  in  molds  of  almost  any  desired  size  and  shape.  Cast  iron,  when 
purified,  forms  wrought  iron,  which  is  soft  and  flexible  but  tough  and 
malleable.  By  various  processes  cast  iron  can  be  converted  into  steel, 
which  possesses  all  the  best  qualities  of  iron.  It  can  be  cast,  hammered, 
rolled  into  railroad  rails,  bars,  beams,  girders,  and  sheets,  and  tempered  for 
cutting  tools  and  springs. 

Iron  is  the  most  widely  diffused  of  metals,  and  iron  ores  are  found  in 
every  land ;  but  the  best  ores,  which  furnish  most  of  the  world's  supply,  are 
mined  in  the  Lake  Superior  region  of  the  "United  States  and  Canada,  in 
Great  Britain,  Germany,  Belgium,  and  Spain.  Sweden  has  immense  masses 
of  high-grade  ore  not  yet  fully  developed.     The  United  States  is  far  in 


CLOTHING  AND   CONSTRUCTIVE  MATERIALS  301 

advance  of  all  other  countries  in  the  production  of  iron  ore,  pig  iron,  and 
steel,  with  Germany  and  Great  Britain  as  second  and  third  in  rank.  The 
quantity  of  iron  used  is  the  best  measure  of  industrial  progress. 

Copper.  —  Next  to  iron,  copper  is  probably  the  most  im- 
portant metal.  It  is  workable,  durable,  and  moderately  hard. 
Before  the  discovery  of  iron  smelting,  bronze,  an  alloy  of  copper 
and  tin,  played  the  part  now  taken  by  iron  and  steel,  and  it  is 
still  used  for  statuary  and  ornamental  work. 

Brass  is  an  alloy  of  copper  and  zinc.  The  peculiar  value  of  copper  lies 
in  the  fact  that  it  is  one  of  the  best  known  conductors  of  heat  and' elec- 
tricity, and  can  be  drawn  into  strong  wire.  Hence  it  is  indispensable  in 
the  development  of  modern  electrical  industry.  The  mines  of  Arizona, 
Montana,  and  Michigan  produce  more  than  half  of  all  the  copper  mined. 
Mexico,  Spain,  and  Japan  rank  next  after  the  United  States. 

Lead.  —  Lead  is  a  soft,  heavy  metal  easily  melted  or  shaped 
in.  the  cold.  It  is  used  for  shot,  bullets,  roofing,  and  plumbers' 
work.     Solder,  pewter,  and  type  metal  are  alloys  of  lead. 

White  lead,  a  compound  of  the  metal,  is  one  of  the  essential  ingredients 
of  good  paint.  Lead  occurs  with  silver  in  Idaho,  Utah,  and  Colorado,  and 
with  zinc  in  Missouri.  The  United  States,  Spain,  Germany,  and  Australia 
produce  three  fourths  of  the  world's  supply. 

Zinc.  —  Zinc  is  a  hard,  white  metal  which  is  not  corroded  by  air  or 
water.  It  is  extensively  used  as  a  coating  for  sheet  steel  to  prevent  it  from 
rusting.  Such  sheets,  under  the  name  of  galvanized  iron,  are  used  for  tanks, 
roofing,  cornices,  spouts,  water  pipes,  and  domestic  utensils.  The  United 
States,  Germany,  and  Belgium  yield  four  fifths  of  the  world's  supply. 

Tin.  —  Tin  is  a  soft,  white  metal  which  was  once  semi-precious  on 
account  of  its  scarcity  and  the  demand  for  it  in  making  bronze.  It  is  very 
useful  in  the  form  of  tin  plate,  which  consists  of  sheets  of  iron  coated  with 
tin  and  used  for  roofing  and  "  tinware."  The  tin  mines  of  Cornwall,  Eng- 
land, have  been  worked  for  2,500  years,  but  the  Malay  Peninsula  and 
neighboring  islands  now  furnish  three  fourths  of  the  supply. 

Aluminum.  —  Aluminum,  the  lightest  of  the  commercial  metals,  is  also 
the  most  abundant,  being  the  base  of  all  clays  and  forming  eight  per  cent  of 
the  earth  crust.  The  difficulty  of  extraction  from  its  ores  makes  it  costly. 
In  color,  luster,  and  polish  it  resembles  tin.  It  does  not  corrode,  is  work- 
able, and  is  a  good  conductor  of  electricity.    It  is  about  one  third  as  heavy 


302 


ECONOMIC   GEOGRAPHY 


as  iron  and  may  be  substituted  for  it  in  places  where  lightness  and  strength 
are  desirable.  Its  workable  ores  are  rare.  The  metal  is  extracted  at 
Niagara  Falls,  New  York,  and  at  several  other  places. 

Mercury.  —  Mercury,  the  only  metal  liquid  at  ordinary  temperatures,  is 
invaluable  in  the  extraction  of  gold  from  its  ores,  in  the  manufacture  of  ther- 
mometers, barometers,  and  other  scientific  instruments,  and  in  silvering 
mirrors.    Spain  furnishes  one  third  and  California  one  fifth  of  the  supply. 

Precious  Metals.  —  Gold  and  silver  are  known  as  precious 
metals  on  account  of  their  high  value.     An  ounce  of  gold  is 

worth  a  little  over 
twenty  dollars,  and 
an  ounce  of  silver 
from  fifty  cents  to 
one  dollar.  For  use 
in  the  arts  gold  is 
inferior  to  copper, 
and  silver  is  inferior 
to  tin.  Their  value 
depends  essentially 
upon  their  beauty, 
which  makes  them 
desired  for  orna- 
ment; hence  gold  is 
the  common  mate- 
rial used  for  jewelry, 
and  silver  for  tableware.  Gold  has  a  rich  yellow  color  and  a 
brilliant  luster  which  does  not  readily  tarnish.  It  is  easily 
workable,  but  too  soft  for  use  unless  alloyed  with  copper  or 
silver  to  harden  it.  Silver  is  white,  less  lustrous  than  gold,  and 
more  easily  tarnished;  hence  it  is  far  inferior  in  value,  although 
more  useful  in  the  arts.  Gold  has  become  the  standard  of 
value  and  a  medium  of  exchange  of  the  civilized  world  and  is 
used  chiefly  for  coinage,  while  silver  is  the  metal  for  coins  of 
less  value. 

Gold  is  found  disseminated  in  veins,  lodes,  or  reefs  of  quartz  and  other 
minerals,  and  in  alluvial  sands  and  gravels.    It  is  separated  by  crushing 


Fig.  280.  —  Washing  gold,  Guiana. 


CLOTHING  AND   CONSTRUCTIVE  MATERIALS 


303 


the  ore,  when  necessary,  washing  out  impurities  with  running  water,  and 
dissolving  the  gold  with  mercury.  Gold  is  extracted  from  low-grade  ores 
by  a  solution  of  potassium  cyanide.  The  world's  output  of  gold  is  about 
$400,000,000  annually,  of  which  South  Africa  produces  about  two  fifths,  the 
United  States  one  fourth,  and  Australia  one  sixth. 

Silver  is  obtained  largely  from  lead  and  gold  ores,  as  well  as  from  ores 
worked  for  silver  alone.  Its  extraction  is  difficult  and  complicated.  The 
amount  mined  is  largely  in  excess  of  gold,  but  its  total  value  is  less.  The 
United  States  and  Mexico  produce  each  about  one  third  of  the  world's 
product. 

Tools.  —  Man  is  the  only  animal  that  uses  tools.  It  is  doubt- 
ful if  apes  and  monkeys,  who  have  hands  and  could  use  tools, 
ever  spontaneously  use  even 
a  stick  or  a  stone  for  any 
purpose.  Primitive  tools 
were  of  the  simplest  charac- 
ter. A  stick,  smoothed, 
straightened,  and  pointed, 
with  the  end  hardened  in  the 
fire  or  tipped  with  an  animal 
tooth,  developed  into  the 
spear  and  harpoon.  A  stone 
thrown    from    the    hand    or 

from  a  sHng  of  bark  or  hide,  a  club  weighted  at  one  end  or 
made  more  effective  by  the  insertion  of  sharp  teeth  or  stones, 
a  flake  of  flint  or  broken  volcanic  glass  with  a  cutting  edge, 
were  the  rude  forerunners  of  the  rifle,  cannon,  ax,  sword,  scythe, 
knife,  and  razor. 

The  invention  of  the  bow  and  arrow  gave  their  possessors  such  an  ad- 
vantage in  range  and  accuracy  of  aim  as  to  rank  in  importance  with  the 
discovery  of  gunpowder.  The  invention  of  pottery,  made  at  first  by  daub- 
ing a  basket  with  clay,  then  molding  the  clay  without  the  basket,  made  it 
possible  to  store  and  carry  liquids  and  to  cook  food  by  boiling.  The  smelt- 
ing of  iron  ore  put  into  men's  hands  at  once  a  superior  material  for  all 
sorts  of  implements,  weapons,  and  utensils,  enabled  them  to  work  wood 
into  boats,  houses,  and  furniture,  and  vastly  to  improve  their  agriculture. 
Chiefly  by  the  utilization  of  wood  and  iron  man  has  arrived  at  his  present 


Fig.  281.  —  Primitive  tools  and  weapons. 


304  ECONOMIC   GEOGRAPHY 

stage  of  economic  development,  in  which  by  the  use  of  machines  he  has 
increased  production  in  an  incalculable  ratio  beyond  what  he  could  do 
with  his  bare  hands.  The  grain  binder  and  thresher,  the  steam  plow,  the 
cotton  gin,  the  power  loom,  the  linotype,  the  cylinder  press,  the  pipe  organ, 
the  electric  crane,  the  steel  steamship,  the  steam  turbine,  the  gas  engine, 
the  dynamo,  the  trolley  car,  the  automobile,  and  the  aeroplane  are  only 
complex  tools  for  doing  work  efl&ciently  and  on  a  large  scale.  They  are 
extensions  and  improvements  of  the  natural  machines,  —  the  human  leg 
and  arm. 

Technical  Materials.  —  The  complex  activities  of  civilized 
men  require  a  vast  variety  of  materials  for  a  vast  variety  of 
purposes.  They  are  derived  from  many  natural  sources  and 
are  artificially  made.  To  describe  them  and  their  uses  in  detail 
would  require  a  large  volume.  The  following  are  some  of  the 
most  important  in  each  class. 

Fertilizers.  —  The  natural  supply  of  plant  food  in  good  soils 
is  generally  sufficient  except  in  nitrogen,  phosphorus,  and  potash 
(p.  145).  Hence  these  elements  are  important  ingredients  of 
artificial  fertiHzers,  and  in  old  and  densely  populated  countries 
their  supply  is  a  serious  problem. 

Nitrogen  is  furnished  by  animal  matter,  and  is  a  constituent  of  common 
stable  manure.  Guano  is  the  dung  of  fish-eating  sea  birds,  which  has 
accumulated  upon  islands  in  the  almost  rainless  region  off  the  coast  of 
Peru,  in  some  places  to  the  depth  of  200  feet.  It  contains  large  percent- 
ages of  both  nitrogen  and  phosphorus,  and  many  million  tons  have  been 
shipped  to  England  and  other  countries  of  western  Europe.  Bat  guano, 
obtained  from  caves,  is  used  for  the  same  purpose.  Chile  saltpeter  (sodium 
nitrate),  containing  a  large  percentage  of  nitrogen,  occurs  in  extensive 
deposits  in  the  desert  of  Atacama  (Peru  and  Chile) ,  and  has  been  mined  and 
exported  to  Europe  for  many  years.  The  supplies  of  guano  and  nitrate  are 
limited  and  exhaustible,  but  the  nitrogen  of  the  air  is  inexhaustible.  It  has 
been  discovered  that  clover,  alfalfa,  peas,  beans,  and  other  plants  of  the  same 
family,  have  upon  their  roots  nodules  containing  bacteria,  or  microscopic 
plants,  which  absorb  and  assimilate  nitrogen  from  the  air.  When  the 
roots  decay  the  nitrogen  becomes  available  for  the  next  crop.  Artificial 
nitrate  is  now  being  made  from  air  and  lime  by  electricity  in  Norway, 
where  water  power  is  cheap.  Thus  the  nitrogen  problem  seems  to  be 
definitely  solved. 


CLOTHING  AND   CONSTRUCTIVE  MATERIALS 


305 


Copyright  by  Doubleday,  Page  &  Co. 

Fig.  282. — Tubercles  on  the  roots  of  soy  bean. 


(Fletcher's  Soils.) 


,  Phosphorus.  —  Animal  matter  generally  contains  phosphorus  as  well  as 
nitrogen,  but  it  is  present  in  large  proportions  in  fish  and  in  the  bones  of 
herbivorous  animals.  Near  the  seashore  fish  which  are  not  fit  for  food 
are  caught  in  nets  and  liberally  applied  to  the  land.  Beds  of  phosphate 
rock  in  southern  United  States  and  other  localities  are  composed  largely 
of  the  teeth  and  bones  of  marine  animals.  Such  deposits  are  of  greater 
real  value  to  the  human  race  than  gold  mines.  The  phosphorus  in  them  is 
in  an  insoluble  form,  and  must  be  chemically  treated  to  make  it  available 
for  plant  food.  Large  quantities  of  phosphatic  fertilizer  are  made  from 
slaughterhouse  refuse  and  the  bones  of  domestic  animals. 

Potash.  —  Wood  ashes  contain  considerable  quantities  of  potash  salts, 
which  are  leached  out  with  water  and  used  in  making  fertilizers,  glass,  and 
soap.     Potash  salts  are  mined  at  Stassfurth,  Germany. 

Salt.  —  Many  chemical  compounds  are  found  in  nature  which 
can  be  utilized  in  their  natural  state.  The  most  important  is 
common  salt  (sodium  chloride).  It  is  obtained  by  the  evapora- 
tion of  sea  water  and  of  other  natural  brines,  such  as  the  water 
of  the  Caspian  Sea,  Great  Salt  Lake  in  Utah,  and  the  Sal  ton 
Lake  of  California. 


3o6 


ECONOMIC   GEOGRAPHY 


Strata  of  rock  salt,  left  by  the  evaporation  of  ancient  seas,  sometimes 

i,ooo  feet  thick,  occur  in  the  earth  crust.     The  solid  salt  is  sometimes 

mined  like  coal,  but  since  it  is 

frequently  impure  it  is  often 

cheaper  to   dissolve  the  salt 

in  water  and   evaporate  the 

brine.    There  are  famous  salt 

mines   in  Poland,    Germany, 

Austria,  Spain,  England,  New 

York,  and  Louisiana.    Salt  is 

used  almost  universally  as  a 

food   and  as   a  preservative. 

It   is   also    the   source   from 

which  many   compounds  are 

manufactured,   among  which 
Fig.  a83.-Salt  works,  France.  ^^^     ^^^^     ^^^^     ^     ^^^^^ 

soap,  glass,  and  baking  powder,  is  the  most  important. 

Sulphur  is  obtained  from  volcanic  regions,  where  it  sublimes  from  the 
hot  rock,  and  by  roasting  pyrite,  a  mineral  common  in  coal  mines.  Sicily, 
Louisiana,  and  Japan  are  the  chief  sources.  It  is  one  of  the  most  important 
of  chemicals,  indispensable  in  the  manufacture  of  matches,  gunpowder,  and 
vulcanized  rubber.  The  fumes  of  burning  sulphur  are  a  cheap  and  efficient 
bleaching  agent  and  disinfectant.  It  is  the  basis  of  manufacture  of  sul- 
phuric acid  and  a  long  series  of  derivative  compounds  which  rival  in  number 
and  variety  of  uses  those  derived  from  common  salt. 

Pigments.  —  Substances  used  to  give  color  to  paint  are  in  some  cases 
natural  minerals  and  in  others  artificial  products.  The  ochres  are  yellow, 
brown,  and  red  compounds  of  iron,  both  natural  and  artificial.  White  lead, 
red  lead,  litharge,  and  chrome  yellow  are  made  from  lead,  zinc  white  from 
zinc,  vermilion  from  mercury,  and  chrome  red  from  chromium. 

Oils.  —  There  are  many  vegetable  oils  in  use  for  food  for 
men  and  animals,  for  soap  and  candle  making,  lubrication, 
illumination,  and  dressing  skins.  Olive  oil  is  the  most  valuable 
and  takes  the  place  of  animal  fat  and  flesh  in  the  Mediterranean 
countries.  Palm  and  coconut  oil  are  products  of  tropical  re- 
gions, and  cottonseed  and  maize  oils  of  temperate.  The  most 
important  animal  fats  and  oils  are  lard  from  hogs  and  tallow 
from  cattle  and  sheep,  used  for  food  and  for  making  soap  and 
candles.     Oil  is  obtained  from  the  menhaden  fish,  and  the  whale 


CLOTHING  AND   CONSTRUCTIVE  MATERIALS  307 

fishery  was  once  the  chief  source  of  illuminating  oils.  Right 
whales  are  now  nearly  exterminated.  Soap  is  made  from  vege- 
table and  animal  fats  by  boiling  them  with  lye  (caustic  soda 
or  caustic  potash).     Glycerin  is  a  by-product. 

Essential  Oils  are  not  fats,  will  not  make  soap,  and  are  soluble  in  water. 
They  are  distilled  from  various  plants  and  are  in  common  use  as  medicines 
and  flavoring  extracts.  Camphor  is  the  only  solid  essential  oil,  and  is 
obtained  entirely  from  the  Japanese  island  of  Formosa.  Oil  of  pepper- 
mint, lemon,  vanilla,  wintergreen,  sassafras,  bitter  almonds,  anise,  cloves, 
and  many  others  are  well  known. 

Resins  and  Gums.  —  Resins  and  gums  are  vegetable  products 
used  in  making  soap,  paint,  varnish,  and  mucilage.  Crude  tur- 
pentine from  the  hard  pine  tree  is  the  most  important.  It  is 
separated  by  distillation  into  spirits  of  turpentine,  used  for 
mixing  paints,  and  rosin,  an  ingredient  of  many  soaps. 

Gum  arabic,  from  the  savannas  of  Africa,  is  the  base  of  mucilage.  Copal, 
dammar,  and  lac,  which  is  produced  by  an  insect,  make  fine  varnishes. 
Chicle,  produced  only  in  Yucatan  and  used  only  in  the  United  States, 
forms  the  body  of  chewing  gum.  Amber  is  a  fossil  gum  from  the  shores 
of  the  Baltic  Sea,  used  for  ornament  and  the  mouthpieces  of  pipes. 

Dyestufifs.  —  Dyestuffs  are  mostly  of  vegetable  origin.  Indigo,  madder, 
and  logwood  are  the  most  important.  The  natural  supply  is  now  almost 
entirely  superseded  by  artificial  dyes,  made  in  great  variety  from  coal  tar. 

The  number  of  useful  commodities,  natural  and  artificial,  has 
probably  never  been  estimated,  but  would  run  into  the  tens  of 
thousands.  The  number  of  kinds  of  articles  procurable  in  any 
civilized  town  of  50,000  inhabitants,  not  including  medicines, 
is  not  less  than  i  ,000. 


CHAPTER   XXI 


HEAT,    LIGHT,    AND    POWER 


wmr 


Heat.  —  The  development  of  civilization  is  characterized  not 
only  by  a  vastly  increased  utilization  of  material  resources, 
but  no  less  by  growing  dependence  upon  immaterial  resources, 
especially  heat,  light,  and  power.  The  discovery  of  the  use  of 
fire,  at  first  accidental  from  lightning  or  a  volcano,  was  a  step 
second  in  importance  to  none  in  the  rise  of  man. 

The  invention  of  methods  for  kindling  fire  when  wanted  has  exercised 
a  marked  influence  upon  human  progress.     The  savage  rubs  two  sticks 

together  until  they  ignite,  — 
a  thing  not  easy  to  do.  Our 
ancestors  of  only  a  century 
ago  depended  upon  sparks 
struck  by  flint  and  steel, 
while  with  us  lucifer  matches 
arc  the  cheapest  and  most 
abundant  of  devices.  While 
artificial  heat  is  not  needed 
for  comfort  in  tropical  re- 
gions, fire  enables  men  to 
cook  food,  and  this  will  al- 
ways be  its  prime  function. 
The  use  of  fire  to  maintain 
bodily  temperature  became 
necessary  as  men  migrated 
into  higher  latitudes  and  al- 
titudes. The  burning  of  brick 
and  pottery,  the  smelting  of 
ores,  the  working  of  metals, 
and  the  manufacture  of  glass  require  the  highest  temperatures  attainable 
by  the  use  of  fuel.  Some  modern  industries,  such  as  the  extraction  of 
aluminum,  are  made  possible  only  by  the  electric  arc  at  6,000°. 

308 


Fig.  284.  —  Savage  kindling  a  fire. 


HEAT,   LIGHT,   AND   POWER.  309 

Light.  —  Artificial  light  is  an  unappreciated  luxury.  Julius 
Caesar  wrote  his  Commentaries  by  the  light  of  a  dull,  smoky 
lamp,  made  by  dipping  a  loose  wick  in  an  open  dish  of  oil. 
In  the  Middle  Ages  houses  and  streets  were  lighted  with  flar- 
ing torches  made  by  burning  various  combustibles  in  an  iron 
basket.  In  the  height  of  the  whale-fishing  industry  sperm-oil 
lamps  gave  a  brilliant  light,  but  were  costly  and  unsafe.  Within 
the  memory  of  men  now  living  the  common  people  had  no  better 
illuminant  than  a  pine  knot  or  a  "  tallow  dip  "  candle.  It  was 
not  until  the  latter  half  of  the  nineteenth  century  that  the  dis- 
covery of  petroleum  gave  to  everybody  a  cheap  and  efficient 
light.  Coal  gas  has  been  used  in  cities  for  lighting  about  a 
century,  and  now  electricity  turns  night  into  day. 

Power.  —  The  ultimate  source  of  nearly  all  the  power  avail- 
able for  doing  work  on  the  earth  is  insolation,  or  radiant  energy 
from  the  sun.  Sunlight  makes  plants  grow,  and  vegetation  is 
the  source  of  food  which  gives  animals  strength,  and  of  fuel 
which,  when  burned,  may  run  a  heat  engine.  The  sun  heats 
different  parts  of  the  atmosphere  unequally  and  thus  makes  the 
wind  blow.  The  sun  evaporates  water  from  the  sea,  which, 
falling  as  rain  on  land,  runs  off  in  streams  which  furnish  water 
power. 

Man  Power.  —  Primitive  man  was  dependent  upon  his  own 
muscles.  He  traveled  and  used  implements  and  weapons,  but 
he  did  not  travel  fast,  build  large  structures,  or  transport  much 
freight.  He  had  only  two  legs  and  two  arms,  both  weak  and 
short,  and  with  them  alone  he  could  not  rise  above  savagery. 
Human  p>ower  and  labor  is  still  indispensable  and  always  will  be. 

The  greatest  amount  of  human  labor  is  employed  in  the  most  advanced 
industrial  communities.  It  has  often  been  thought  that  machines  would 
do  away  with  human  labor,  but  they  generally  increase  the  number  of  per- 
sons that  can  find  employment  and  the  total  amount  of  muscular  energy 
expended.  This  is  true  in  manufacturing  industries  and  transportation. 
Agriculture  seems,  so  far,  to  be  an  exception  to  the  rule.  The  use  of 
agricultural  machinery  reduces  the  number  of  laborers  employed,  and  exclu- 
sively rural  districts  are  decreasing  in  population.     This  may  be  a  tem- 


310  '      ECONOMIC   GEOGRAPHY 

porary  phase,  to  be  followed  by  the  reverse  as  agriculture  becomes  more 
scientific  and  intensive. 

Labor  Supply.  —  The  problem  of  obtaining  a  sufficient  supply  of  un- 
skilled human  labor  is  one  of  the  most  serious  which  confronts  the  civilized 
world  to-day.  For  the  most  rapid  advancement  labor  should  be  plentiful, 
but  the  supply  probably  never  will  equal  the  demand.  FaciHties  for  cheap 
transportation  render  possible  a  circulation  of  labor,  the  people  of  those 
countries  which  have  a  surplus  migrating  to  those  which  have  a  deficiency, 
Indian  coolies  are  transported  to  South  Africa  to  work  in  the  gold  mines, 
and  Jamaica  negroes  to  Panama  to  dig  the  canal.  Three  hundred  thou- 
sand Italians  come  to  the  United  States  in  a  single  year,  one  third  of  whom 
return  to  Italy  sooner  or  later.  Thousands  cross  the  sea  to  work  in  Amer- 
ica during  the  season  or  as  long  as  the  job  lasts,  and  go  back  home  when 
business  is  dull.  The  United  States,  Canada,  Australia,  and  South  Africa, 
young  and  growing  countries,  need  the  largest  supply  of  unskilled  labor. 
Great  Britain,  France,  and  Germany  are  now  self-sufficing,  and  Spain,  Por- 
tugal, Italy,  and  Austria-Hungary  have  a  surplus ;  but  as  these  countries 
develop  they  will  not  continue  in  such  a  condition.  Russia,  the  Balkan 
countries,  India,  China,  the  East  and  West  Indies,  and  north  and  central 
Africa  have  a  large  surplus  of  labor.  The  African  supply  increases  under 
civilized  control,  and  the  abolition  of  war  and  slavery;  but  the  people  often 
lack  efficiency,  are  difficult  to  control,  are  unaccustomed  to  manual  labor, 
and  have  a  high  death  rate.  These  defects  are  characteristic  of  the  natives 
of  tropical  countries  generally.  The  people  of  northern  India  are  industrious 
and  of  good  physique,  but  race  and  religious  prejudices,  and  sensitiveness 
to  climate  interfere  with  their  transference  to  other  countries.  The  people 
of  south  and  Asiatic  Russia,  the  Balkan  states,  and  the  Turkish  Empire  are 
semi-European,  but  rather  unintelligent.  The  Chinaman  is  docile,  peace- 
able, hardy,  easy  to  feed,  and  of  high  efficiency.  He  does  not  assimilate  with 
other  peoples,  and  the  white  man's  prejudice  against  him  is  so  strong  that 
he  is  excluded  by  law  from  the  United  States  and  Australia,  where  a  large 
supply  of  labor  is  most  needed. 

Animal  Power.  —  Domestic  animals  lifted  men  out  of  savagery. 
America  remained  barbarous  for  centuries  largely  because  of  the 
lack  of  domestic  animals.  Many  of  the  larger  animals  are  used 
more  or  less  for  power,  but  the  horse  is  the  most  generally  efficient. 
The  early  civilization  of  Eurasia  was  largely  the  result  of  horse 
power  used  for  mobility  and  transportation.  The  horse  survives 
the  introduction  of  mechanical  and  chemical  power  in  agri- 


HEAT,   LIGHT,   AND    POWER 


311 


culture,  trade,  and  war,  but  his  importance  is  relatively  de- 
clining. The  time  may  come  when  he  will  be  excluded  from 
cities  and  used  more  for  pleasure  than  for  business. 

Wind  Power.  —  There  is  no  lack  of  wind  power  in  any  part 
of  the  world  except  the  calm  belts,  and  it  is  inexhaustible. 
Until  a  century  ago  all  large 
vessels  were  propelled  by  the 
wind,  and  sailing  vessels  still 
comprise  about  one  eighth  of 
the  world's  shipping.  Wind 
power  is  used  in  Holland  and 
the  United  States  in  small 
units  for  pumping  water  and 
grinding  grain.  Its  use  is  re- 
stricted only  by  its  incon- 
stancy. If  means  are  ever 
devised  by  which  power  can 
be  cheaply  stored  for  use 
during  a  calm,  the  wind  may 
yet  drive  the  machinery  and 
do  the  work  of  the  world. 

Fuel.  —  The  use  of  power  from  sun  heat  stored  in  vegetable 
matter  was  made  possible  by  the  invention  of  the  steam  engine, 
which  is  really  a  heat  engine.  It  was  first  made  practical  by 
Watt,  about  1770,  and  was  successfully  applied  to  vessels  by  Ful- 
ton, in  1807,  and  to  land  locomotives  by  Stephenson  between  181 5 
and  1830.  The  importance  of  its  effects  cannot  be  calculated. 
By  it  man's  legs  and  arms  have  been  multipHed,  lengthened, 
and  strengthened  enormously.  It  has  made  world  commerce 
and  world  power  possible.  For  all  practical,  human  purposes, 
it  has  reduced  the  size  of  the  earth  to  about  one  tenth  its 
former  dimensions,  and  has  correspondingly  promoted  the  unity 
of  mankind,  making  all  men  neighbors. 

Wood  has  always  been  the  fuel  most  used  for  domestic  purposes,  and 
the  boilers  of  the  first  steam  engines  were  heated  with  wood.     While  forests 


Fig.  285.  — Windmill,  Holland. 


312 


ECONOMIC   GEOGRAPHY 


are  more  valuable  for  construction  than  for  fuel,  the  world's  supply  of 
wood  of  little  value  for  anything  else  than  to  burn  is  very  large. 

Peat.  —  When  vegetable  matter  decays  under  water  it  is  converted  into 
a  brown  or  black,  spongy  mass,  called  peat,  muck,  or  turf.  A  cool,  moist 
climate  is  most  favorable  for  its  formation,  and  it  has  accumulated  in  the 
glacial  lake  beds  and  bogs  of  northern  Europe  and  America  in  large  but 
unmeasured  quantities.  When  dried  it  forms  as  good  fuel  as  wood,  and 
in  countries  where  coal  and  wood  are  scarce  peat  is  in  common  use.  It  is 
sometimes  pressed  by  machinery  into  briquettes  and  used  for  industrial 
purposes.  Russia,  Germany,  Sweden,  Denmark,  Holland,  and  Ireland  are 
peat-using  countries. 


Coal.  —  Coal  is  fossil  fuel,   the   concentrated  residue  of  a 
luxuriant  vegetation  which  flourished  millions  of  years  ago.     It 

was  first  converted  into  peat, 
then  buried  under  accumula- 
tions of  sediment,  and  trans- 
formed by  heat  and  pressure 
into  coal.  Lignite,  or  brown 
coal,  has  iDeen  changed  so 
little  as  to  retain  the  appear- 
ance of  wood,  and  has  about 
half  the  fuel  value  of  the  best 
coal.  Very  extensive  beds  of 
lignite  exist  in  the  United 
States  and  other  countries, 
but  are  as  yet  little  used. 
Bituminous  or  soft  coal,  con- 
Fig.  286. -Coal  mine.  taiuiug   from    6o   to   85   per 

cent  of  carbon,  is  widely  distributed,  and  the  world's  main  re- 
liance for  industrial  fuel.  Large  quantities  are  converted  by 
heating  into  coke,  which  resembles  anthracite.  It  is  also  the 
source  of  illuminating  gas.  Anthracite  or  hard  coal  contains 
from  85  to  98  per  cent  of  carbon,  and  is  of  the  highest  value 
for  most  purposes.  The  area  of  the  coal  fields  of  the  world  is 
estimated  at  650,000  square  miles,  of  which  two  fifths  belong  to 
the  United  States  and  one  third  to  China. 


HEAT,    LIGHT,   AND   POWER 


313 


The  yield  of  coal  per  square  mile  is  very  variable,  the  seams  in  some 
areas  being  few  and  thin,  and  in  others  numerous  and  thick.  Coal  is 
mined  in  England  to  a  depth  of  over  half  a  mile.  The  world's  output  is 
about  1,200  million  tons  annually,  of  which  the  United  States  mines  about 
two  fifths,  Great  Britain  one  fourth,  and  Germany  one  fifth.  About  half 
of  it  is  used  for  power  purposes.  Coal  and  iron  form  the  basis  of  modern 
industrial  civilization.  In  the  production  and  consumption  of  both  these 
articles  per  capita,  the  United  States,  Great  Britain,  Belgium,  and  Germany 
are,  in  that  order,  the  leading  countries. 


Fig.  287.  —  Coal-producing  regions. 


The  British  coal  fields  are  small  in  area  but  very  rich,  and 
have  been  the  chief  source  of  British  wealth  and  sea  power. 
In  the  fourteenth  century  the  use  of  coal  in  England  was  pro- 
hibited by  law  on  account  of  supposed  injury  to  health.  Now 
ten  millions  of  people  are  hving  in  British  coal  fields  to  make 
use  of  it.  The  anthracite  or  "  smokeless  coal  "of  south  Wales 
is  used  for  war  vessels,  and  for  smelting  ores  sent  from  distant 
lands  for  that  purpose. 

The  exhaustion  of  the  British  coal  supply  in  the  near  future  is  a  serious 
question.  The  present  century  may  see  it  so  far  reduced  as  to  render 
British  competition  with  manufacturers  elsewhere  difficult  or  impossible. 
On  the  continent  of  Europe  coal  of  generally  medium  or  inferior  quality 
exists  in  strips  and  patches  from  Belgium  to  the  Black  Sea.  The  coal 
fields  of  China  are  very  large  and  rich,  but  as  yet  wholly  undeveloped. 


3U 


ECONOMIC   GEOGRAPHY 


The  southern  continents  are  poorly  suppHed  with  coal,  Australia  being 
most  highly  favored.  While  coal  occurs  in  all  lands  from  Greenland  to 
Antarctica,  North  America  perhaps  contains  as  much  coal  as  all  the  rest  of 
the  world.  The  principal  coal  fields  are  (i)  the  Appalachian,  from  Nova 
Scotia  to  Alabama;  (2)  the  Interior,  from  Ohio  to  Kansas  and  from  Texas 
to  Alberta;  and  (3)  the  Pacific,  from  Washington  to  Alaska.  Anthracite  is 
confined  to  eastern  Pennsylvania  and  a  few  patches  in  the  Rocky  Moun- 
tains. On  account  of  easily  available  coal  and  iron,  great  manufacturing 
industries  have  grown  up  around  Pittsburgh,  Cleveland,  and  Chicago,  and 
the  urban  industrial  and  commercial  district  of  the  Atlantic  seaboard  is 
near  the  coal  fields.  The  remarkable  development  of  railroads  in  the 
United  States  and  Canada  is  largely  due  to  the  wide  distribution  of  coal. 
The  consumption  of  coal  in  the  United  States  nearly  doubled  in  the  ten 
years  from  1900  to  1910.  No  coal  is  being  formed  in  the  earth  at  the 
present  time,  and  the  supply  cannot  be  anywhere  inexhaustible.  At  the 
present  rate  of  increase  of  consumption,  the  world's  store  may  be  used 
up  in  500  or  1,000  years.  Its  duration  will  probably  be  prolonged  by  the 
increased  use  of  other  sources  of  power. 

Petroleum.  —  Rock  oil  is  a  product  of  the  natural  decompo- 
sition of  organic  matter  in  deep-seated  strata  of  the  earth  crust, 


I 


Fig.  288.  —  Oil  wells  and  tanks,  Russia. 


and  is  obtained  from  wells.  It  is  not  found  in  the  same  strata 
with  coal.  Of  the  280  million  barrels  consumed  annually,  the 
United  States  produces  nearly  two  thirds  and  the  Caspian  field 
in  Russia  more  than  one  fifth. 


HEAT,   LIGHT,   AND   POWER  315 

Oklahoma,  California,  Illinois,  Texas,  Ohio,  West  Virginia,  and  Pennsyl- 
vania are  important  oil-producing  states.  Much  oil  is  pumped  through 
underground  pipe  lines  to  refineries  at  Cleveland,  Toledo,  and  Whiting, 
Ind.,  and  to  the  Atlantic  coast  cities.  Petroleum  is  used  in  its  crude  form 
as  fuel  for  engines,  but  it  is  refined  by  distillation  into  a  large  number  of 
products,  the  most  important  of  which  are  kerosene,  gasoline,  lubricating 
oils,  and  paraffin.  Kerosene  is  the  cheapest  and  most  efficient  illuminant 
the  world  has  ever  known.  Gasoline  has  recently  attained  prime  impor- 
tance for  power  by  the  development  of  the  internal-combustion  or  gas 
engine,  which  is  especially  adapted  for  small  units,  and  is  displacing  the 
steam  engine  for  many  purposes.  As  a  liquid  fuel  easily  converted  into  a 
gas  it  has  no  rival  except  alcohol. 

Natural  Gas.  —  Gas  is  the  most  convenient  form  of  fuel,  and 
a  cheap  and  abundant  siipply  of  it  is  of  great  value.  Gas  made 
artificially  by  heating  coal  has  long  been  used  for  lighting  and 
cooking,  but  its  cost  precludes  its  general  use.  Natural  gas, 
produced  by  the  distillation  of  organic  matter  in  the  earth 
crust,  is  of  general  occurrence  in  connection  with  petroleum. 

Burning  springs  have  attracted  attention  in  many  countries  since  the 
earliest  times.  Those  on  the  shores  of  the  Caspian  Sea  have  been  objects 
of  veneration  by  the  Persian  fire  worshipers  since  a  period  before  the 
Christian  era.  About  1886  gas  began  to  be  obtained  in  large  quantities 
from  wells  in  Pennsylvania,  Ohio,  and  Indiana,  and  used  for  lighting, 
heating,  and  industrial  purposes.  It  was  conducted  in  pipes  to  towns 
within  200  miles  of  the  wells,  and  the  "  gas  belt  "  became  a  busy  manu- 
facturing region,  especially  of  those  articles  requiring  high  temperatures, 
such  as  glass,  tin  plate,  brick,  pottery,  and  steel  specialties.  West  Vir- 
ginia, Illinois,  and  Kansas  also  became  prominent  gas-producing  states. 
Half  the  gas  was  wasted,  and  the  supply  for  manufacturing  and  general 
heating  was  practically  exhausted  in  about  twenty  years.  In  some  cases 
gas  was  followed  by  petroleum  in  the  same  fields  and  wells,  and  finally 
both  were  displaced  by  salt  water. 

Explosives.  —  Gunpowder,  giant  powder,  nitroglycerin,  dynamite,  cordite, 
and  other  high  explosives  are  fuels  which  burn  rapidly  and  suddenly  liberate 
large  volumes  of  gas,  and  are  used  in  hunting,  war,  and  blasting  rock. 

Water  Power.  —  The  power  of  water  to  drive  machinery  is 
proportional  to  the  quantity  and  the  head  or  height  of  fall. 
Natural  cataracts  in  large  streams  furnish  most  power,  but  are 


3i6 


ECONOMIC   GEOGRAPHY 


not  always  most  available.     Dams  are  constructed  to  concen- 
trate the  fall  at  one  place  and  to  store  water,  and  are  most 

efficient  in  streams  of 
steep  slope  and  narrow 
valleys,  like  those  of  New 
England.  Good  water 
powers  are  abundant  in 
mountainous  regions,  re- 
mote from  centers  of  pop- 
ulation, but  the  develop- 


Fig.  289.— Water  wheel,  Georgia. 

ment  of  electrical  science  has  made 
such  power  more  available. 

Electricity  is  not  a  source  of  power,  but  a 
convenient  form  in  which  power  can  be  dis- 
tributed. The  cars  of  city  and  interurban 
lines  are  run  by  electricity  generated  at  one 
or  more  power  stations  and  transmitted  over 

copper  wires.  Water  power  is  used  to  generate  electricity,  which  is  used 
to  do  work  at  places  sometimes  200  miles  distant.  The  greatest  source  of 
hydro-electric  power  now  in  use  is  Niagara  Falls  (pp.  93,  94,  loi).  As  coal 
becomes  more  scarce  and  costly,  mountainous  countries,  such  as  Italy, 


TIail  Jiiitew- 


Fig.  290.  —  Arrangement  of  hydro- 
electric machinery  at  Niagara 
Falls. 


317 

Switzerland,  and  Norway,  will  become,  by  the  use  of  water  power,  or 
''  white  coal,"  important  centers  of  industry. 

Wave  and  Tidal  Power.  —  The  movement  of  waves  and  the  rise  and 
fall  of  tides  are  possible  sources  of  power,  but  on  account  of  inconvenience 
and  uncertainty  they  are  httle  used. 

Metals.  —  Some  metals,  chiefly  zinc,  iron,  lead,  and  copper,  are  used 
in  electric  batteries  to  generate  power  for  special  purposes,  but  are  too 
costly  for  use  on  a  large  scale.  Radium  and  the  group  of  allied  metals 
recently  discovered  are  capable  of  liberating  enormous  quantities  of  power. 
They  are  now  extremely  rare  and  costly,  but  suggest  interesting  possibili- 
ties for  the  future. 

Solar  and  Terrestrial  Heat.  —  To  contrive  a  system  of 
lenses  and  mirrors  by  which  the  direct  rays  of  the  sun  may  be 
so  concentrated  as  to  become  commercially  available  for  heat, 
light,  and  power  has  been  the  dream  of  engineers,  but  has  never 
yet  been  realized.  The  internal  heat  of  the  earth  is  second 
in  quantity  only  to  that  received  from  the  sun.  If  any  means 
could  be  devised  for  utilizing  it,  it  would  be  sufficient  for  human 
needs  as  long  as  the  earth  remains  inhabitable.  Perhaps  the 
source  of  the  power  of  the  distant  future  will  be  in  the  nature 
of  an  artificial  geyser  or  volcano. 


CHAPTER   XXII 
MANUFACTURE,   TRADE,   AND    TRANSPORTATION 

Manufacture.  —  Nearly  all  natural  products  must  be  more 
or  less  modified  artificially  to  render  them  serviceable  to  man. 
In  low  stages  of  culture  all  of  this,  and  in  all  stages  much  of  it, 
is  done  literally  by  hand.  With  the  progress  of  the  industrial 
arts,  a  larger  and  larger  portion  is  done  by  tools  and  machines, 
which  are  extensions  and  improvements  of  the  human  hand. 

In  simple  societies  each  family  or  group  does  this  work  for  itself  and 
at  home.  In  more  advanced  and  densely  populated  countries  a  division  of 
labor  arises  by  which  an  individual  or  family  makes  some  special  article 
at  home  for  hire  or  for  sale  and  exchange.  Sometimes  a  traveling  artisan 
goes  from  house  to  house  to  make  shoes  or  clothes.  These  phases  of 
domestic  manufacture  prevailed  until  the  introduction  of  machinery  and 
mechanical  power.  These  made  necessary  the  capitalistic  or  cooperative 
factory,  in  which  an  individual  or  company  provides  a  large  building 
equipped  with  machines  and  employs  many  operatives  to  work  in  it  for 
wages.  The  distribution  of  hydro-electric  power  has  brought  about  in 
some  places  and  industries  a  partial  return  to  domestic  manufacture,  in 
which  individuals  or  small  groups  operate  machines  at  home. 

Conditions  of  Manufacture.  —  To  make  any  line  of  goods  on 
a  large  scale  with  profit  many  conditions  are  necessary.  Build- 
ings, machinery,  power,  heat,  and  raw  materials  must  be  sup- 
plied at  the  plant.  A  sufficient  supply  of  skilled  labor  must 
exist  in  the  immediate  neighborhood.  Since  factory  hands  can 
produce  little  or  no  food,  a  sufficient  food  supply  must  be 
within  reach.  Lastly,  the  manufactured  goods  must  be  got  to 
market.  The  location  of  a  successful  factory  is  determined  by 
all  of  these  conditions. 

If  the  raw  material  is  bulky,  it  costs  too  much  to  transport  it  far,  and 
it  is  manufactured  near  the  supply.    This  is  the  case  with  sugar  cane, 

318 


MANtlFACTtrkE,   TRADE,    AND   TRANSPORTATION  319 


from  which  the  sugar  is  extracted  on  the  plantation,  but  shipped  long  dis- 
tances to  be  refined.  Grain  is  threshed  on  the  farm,  but  may  be  sent  any 
distance  to  a  mill.  South  American  hides  are  tanned  in  Massachusetts 
because  capital,  skilled  labor,  tanning  materials,  and  a  market  for  leather 
exist  there  more  abundantly  than  in  Argentina.  The  manufacture  of 
cotton,  wool,  and  silk  is  largely  independent  of  the  place 
of  production  of  the  raw  fibers,  and  is  carried  on  where 
power,  skilled  labor,  capital,  and  markets  combine  to 
make  it  profitable.     Half  the  cotton  grown  in  the  United 


Fig.  291.  —  Factories.     Manchester,  N.  H.     On  the  Merrimac  River. 

States  is  sent  to  England  to  be  made  into  cloth.  The  manufacture  of  iron 
and  steel  involves  the  use  of  very  heavy  materials  —  ore,  coke,  and  lime- 
stone. It  is  carried  on  where  the  three  can  be  brought  together  at  least 
expense  and  the  products  find  a  ready  market,  as  in  western  Pennsylvania, 
eastern  Ohio,  and  northern  Illinois.  The  higher  the  value  of  the  finished 
goods  the  less  dependent  is  their  manufacture  upon  any  conditions  ex- 
cept skilled  labor.  The  most  general  and  potent  control  of  the  location 
of  manufactures  is  transportation.  Great  seaports  such  as  London  and 
New  York,  and  lake  ports,  river  ports,  and  railroad  centers  such  as  Cleve- 
land, Chicago,  Cincinnati,  and  St.  Louis,  attract  all  kinds  of  manufacture, 
because  of  the  facility  with  which  everything  needed  may  be  obtained  and 
the  goods  sent  to  market.  Great  Britain  is  an  example  of  the  same  thing 
on  the  largest  scale  Having  power,  labor,  and  capital  at  home,  by  the  pos- 
session of  a  vast  merchant  marine  and  a  navy  which  commands  the  sea, 
the  British  people  have  grown  rich  by  importing  nearly  all  their  food  and 


3^0  ECONOMIC   GEOGRAPHY 

raw  materials  from  the  ends  of  the  earth  and  sending  their  products  to  all 
the  markets  of  the  world. 

The  United  States  is  by  far  the  greatest  manufacturing  coun- 
try in  the  world,  the  total  value  of  its  products  amounting  to 
15,000  million  dollars  annually.  In  respect  to  area  it  should  be 
compared  with  all  Europe,  and  in  respect  to  population  with  Ger- 
many and  Great  Britain  combined.  Great  Britain  is  second  in 
value  of  total  product,  Germany  third,  and  France  fourth,  but 
Belgium  and  Denmark  each  exceeds  Germany  and  France  in 
value  per  capita. 

Trade.  —  The  most  general  fact  learned  from  a  study  of 
physical  and  economic  geography  is  that  natural  conditions  and 
resources,  and  human  life  and  culture,  differ  in  different  parts  of 
the  world.  The  differences,  both  in  kind  and  degree,  are  almost 
innumerable.  Differences  in  natural  conditions — land,  water,  re- 
lief, soil,  cHmate,  and  the  rest  —  involve  differences  of  resources, 
and  these  in  turn  determine  occupations,  products,  and  modes 
of  human  economy.  It  is  the  business  of  geography  to  study 
and  explain  the  relationships  which  natural  conditions  and  re- 
sources bear  to  human  economies. 

Few  if  any  countries  can  supply  anywhere  near  all  the  products  which 
its  inhabitants  want  and  can  use.  It  would  be  futile  to  try  to  raise  corn 
and  cotton  in  England,  sugar  cane  in  Canada,  or  coffee  and  spices  in  the 
United  States.  Italy  has  no  coal  or  gold,  and  Switzerland,  Holland,  Den- 
mark, and  Ireland  have  no  ores  of  any  kind.  Every  community  can  fur- 
nish, raise,  or  manufacture  some  things  to  better  advantage  than  others, 
and  the  community  which  undertakes  to  be  independent  and  supply  every- 
thing it  needs,  without  help  from  other  communities,  will  be  obliged  to 
limit  its  wants,  which  means  a  relatively  low  stage  of  culture  and  comfort. 
Out  of  these  conditions  arises  trade,  commerce,  or  the  exchange  of  com- 
modities between  different  individuals,  families,  communities,  and  countries. 
Trade  is  the  most  complex  and  important  of  all  the  adaptations  to  his 
environment  which  man  has  accomplished. 

Transportation.  —  All  trade  depends  upon  the  transportation 
of  goods  from  one  place  to  another,  and  has  developed  with  the 
increase  of  facilities  for  transportation.     Methods  of  transporta- 


MANUFACTURE,    TRADE,   AND    TRANSPORTATION  32 1 


Fig.  292.  —  Porters,  China. 


tion  are  either  animal  or  mechanical,  or  a  combination  of  the 
two. 

Porterage.  —  The  simplest  form  of  transportation  is  porterage, 
in  which  loads  are  carried  by  men's  hands  and  arms,  or  on  their 
backs  or  heads.  Although  it  is  inefficient  and  expensive,  it  in- 
creases in  amount  with  the 
increase  of  trade.  The  initial 
and  the  final  movement  of 
goods  will  always  be  chiefly 
by  hand,  as  coal  is  shoveled 
into  the  car  in  the  mine  and 
into  the  furnace  in  the  house. 

Porterage  prevails  among  sav- 
age peoples,  in  tropical  forests  and 
savannas,  and  in  mountainous 
countries.  Among  the  North 
American  Indians  the  men  killed  the  game,  while  the  squaws  brought  in  the 
meat,  and  carried  the  tents,  utensils,  and  babies  on  their  backs.  In  central 
Africa  negro  porters  are  the  chief  reliance.     About  thirty  men  are  required 

to  carry  a  ton  twenty-five  miles  a 
day,  and  they  must  be  fed.  The 
cost  of  transportation  from  the 
Guinea  coast  to  Lake  Tchad,  about 
600  miles,  is  $360  a  ton.  The  cost 
on  the  Uganda  railway  for  nearly 
the  same  distance  is  ten  cents  a 
ton.  In  the  high  Alps  every  peas- 
ant man,  woman,  and  child  carries 
a  loaded  basket  fastened  to  the 
shoulders. 

Pack  Animals.  —  Animals 
arc  a  great  improvement  on 
the  human  porter,  and  the 
dog,  ass,  mule,  horse,  ox, 
camel,  and  elephant  are  all  used  as  beasts  of  burden  (Figs.  256, 
293).  Probably  the  camel  is  the  most  efficient,  carrying  a  load 
up  to  1,000  pounds.    Caravans  of  13,000  camels,  carrying  goods 


Fig-  293. — Loaded  camels,  Egypt. 


322 


ECONOMIC   GEOGRAPHY 


of  a  total  value  of  $800,000,  cross  the  Sahara,  occupying  two 
years  for  a  round  trip. 

Vehicles.  —  Vehicles  propelled  by  man  or  animal  power  are 
the  first  and  simplest  of  mechanical  aids  to  transportation. 

The  North  American  Indians 
used  the  travois,  consisting  of  two 
poles  fastened  to  a  dog's  or  horse's 
back  with  ends  dragging  on  the 
ground.  Cross  pieces  furnished  a 
bed  for  carrying  a  load.  The  in- 
vention of  the  wheel  was  a  great 
step  in  advance,  and  led  to  the 
development  of  innumerable  vehi- 
cles, from  the  Chinese  wheelbar- 
row to  the  railroad  car  and  the 
Fig.  294.  —  Straw-covered  bullock  cart,  Ceylon.    q,jf struck 

Roads.  —  The  use  of  wheeled  vehicles  renders  necessary  the 
construction  of  roads,   of  which  the  modem  railroad  is  the 


Fig.  295.  —  St.  Gothard  coach  road,  Switzerland. 

most  highly  perfected.     An  ideal  road  must  be  smooth,  hard, 
and  level.     These  conditions  are  more  or  less  fully  obtained  by 


MANUFACTURE,   TRADE,    AND   TRANSPORTATION 


323 


grading,  or  cutting  down  elevations  and  filling  depressions  to 
reduce  the  slope  as  much  as  possible,  and  by  surfacing  the  road 
with  wood,  gravel,  stone,  brick,  asphalt,  cement,  or  steel.  Rivers 
and  straits  '  are  crossed 
by  bridges  or  tunnels. 
Mountain  barriers  are 
overcome  by  long  de- 
tours, loops,  and  zigzags 
to  lengthen  the  line  and 
reduce  the  slope,  and 
often  by  a  tunnel  at  the 
summit  (Figs.  295,  296). 

The  Forth  bridge  in  Scot- 
land, the  East  River  bridges 
at  New  York,  the  bridge 
across  the  St.  Lawrence  at  Montreal,  and  several  across  the  Mississippi 
are  among  the  largest  and  most  costly  structures  erected  by  man.  Even 
these  are  surpassed  in  magnitude  and  difficulty  of  engineering  by  the  Mt. 


Fig.  296.  —  Mouth  of  tunnel,  St.  Gothard  railway. 


^^^^■^^Bli^^^L"^  ^^^B" "-"- 

Fig.  297. — Forth  bridge,  Scotland. 

Cenis,  St.Gothard,  and  Simplon  tunnels  in  the  Alps  and  the  Hudson  River 
tunnels  at  New  York.    A  tunnel  under  the  English  Channel  is  seriously 


324 


ECONOMIC   GEOGRAPHY 


planned,  and  one  under  Bering  Strait  proposed.     The  Rocky  Mountains 
and  the  Alps  are  crossed  by  many  railroads,  and  the  Andes  by  one. 

The  railway  mileage  of  the  world  is  over  600,000  miles,  of 
which  North  America  has  nearly  one  half  and  Europe  one 
third.  The  network  of  railroads  is  much  more  dense  in  eastern 
United  States  and  western  Europe  than  elsewhere.  Belgium 
and  the  Netherlands  have  the  greatest  density,  or  the  largest 
mileage  per  square  mile  of  area.  The  longest  and  most  numer- 
ous railroad  lines  extend  east  and  west.  Eight  transcontinental 
lines  cross  North  America  and  one  crosses  northern  Eurasia. 
A  north-south  ^'  pan-American  "  hne  from  Canada  to  Argentina, 
and  a  "  Cape  to  Cairo  "  line  in  Africa  are  probabilities  of  the 
near  future.  The  development  of  the  gas  engine  and  the  auto- 
mobile has  given  a  new  impetus  to  road  construction  for  vehicles 
of  moderate  size. 

Water  Transportation.  —  Transportation  by  water  is  easier 
and  cheaper  than  by  land.  Its  advantages  are  that  water 
surfaces  are  level,  or,  in  the  case  of  navigable  rivers,  have  a 
gentle  slope.     There  is  generally  no  expense  for  construction 

and  maintenance,  friction 
and  resistance  are  small, 
the  vehicles  may  be  very 
large,  and  the  power  re- 
quired for  a  given  load  is 
less  than  on  land. 

Boats  of  many  kinds  are 
in  use,  from  the  single  log  or 
raft,  inflated  oxhide,  dugout, 
canoe,  and  rowboat  to  the 
modern  steamship  of  40,000 
tons  burden,  steaming  600  miles  a  day  and  burning  a  ton  of  coal  per  mile. 
The  growth  of  ocean  trade  has  led  to  the  construction  of  ship  canals,  of 
which  the  Suez  and  the  Panama  are  the  most  important  (pp.  158,  159). 
The  Atlantic  Ocean,  surrounded  by  important  peoples,  is  most  used.  The 
Indian  is  a  connecting  link  between  the  Atlantic  and  the  Pacific,  and  the 
Pacific  is  the  ocean  of  the  future.     Half  the  ocean  commerce  of  the  world 


Fig.  298.  —  Dugout,  with  outriggers,  Philippines. 


MANUFACTURE,   TRADE,   AND   TRANSPORTATION  325 

is  carried  on  between  Europe  and  North  America,  one  eighth  between 
Europe  and  the  Orient  and  Australia  (Suez  route),  and  one  eighth  between 
Europe  and  Africa. 

The  St.  Lawrence  River,  with  its  connecting  lakes  and  canals,  furnishes 
the  greatest  inland  waterway.  The  great  possibilities  of  the  Amazon  and 
the  Kongo  are  as  yet  little  utilized.  The  Mississippi  may  regain  the  trade 
lost  for  want  of  improvement.  The  civilized  world  has  entered  upon  an 
era  of  water  transportation,  and  the  development  of  waterways  is  one  of 
the  great  economic  problems  of  the  twentieth  century. 


Ll  J I 


Fig.  299.  —  Ocean  steamer :  the  Olympic. 

World  Trade. — The  larger  part  cf  the  world's  trade  is  domes- 
tic, consisting  of  an  exchange  of  goods  between  the  different 
parts  of  the  same  country.  It  is  impossible  to  estimate  its 
total  amount.  Of  foreign  commerce,  or  the  exchange  of  goods 
between  different  countries,  an  account  can  be  made  with  con- 
siderable accuracy.  The  value  of  all  the  goods  exchanged  be- 
tween nations  is  about  28,000  million  dollars  annually,  of  which 
the  trade  of  Europe  is  64  per  cent,  America  18  per  cent,  Asia  11  per 
cent,  and  Africa  4  or  5  per  cent.  Among  nations  Great  Britain 
leads  with  20  per  cent,  and  is  followed  by  Germany  with  14 
per  cent,  United  States  with  11  per  cent,  and  France  with  8  per 
cent.  The  little  countries  of  the  Netherlands  and  Belgium 
have  the  largest  foreign  commerce  in  proportion  to  population. 

In  trade  there  are  two  great  movements,  one  in  a  north- 


326  ECONOMIC   GEOGRAPHY 

south  direction  between  the  temperate  regions  and  the  tropics, 
and  one  in  an  east-west  direction  between  temperate  countries 
in  different,  stages  of  development.  At  present  the  east-west 
movement  is  greater,  but  it  may  not  always  remain  so. 

The  present  supremacy  of  the  temperate  zone,  due  to  coolness  and  health- 
fulness,  may,  by  the  control  of  disease  and  the  use  of  artificial  refrigeration, 
pass  to  the  tropics.  Men  may  devise  means  of  keeping  cool  in  the  torrid 
zone  as  they  have  of  keeping  warm  in  the  frigid.  Power  and  raw  materials 
are  plentiful  in  tropical  regions,  and  centers  of  industry  and  population 
may  shift  toward  the  equator. 

Summary.  —  Every  natural  resource  has  existed  upon  the 
earth  since  the  first  appearance  of  man,  and  no  natural  resource 
has  yet  been  fully  utilized.  Probably  natural  resources  exist 
of  which  mankind  is  still  ignorant.  Every  human  want,  art, 
and  economy  had  its  simple  beginnings  in  the  lowest  stages 
of  savagery  and  has  persisted  through  all  stages  of  culture. 
As  each  want,  art,  and  economy  developed,  it  has  influenced 
more  and  more  every  other.  The  development  of  civilization 
and  scientific  economy  has  not  released  men  from  dependence 
upon  natural  resources,  but  only  multiplied  the  number  and 
increased  the  complexity  of  such  relations.  Modern  industrial 
civilization  is  as  truly  based  upon  grass,  trees,  coal,  iron,  and 
copper  as  Eskimo  life  upon  snow,  seals,  and  walrus. 

The  most  favored  countries  possess  lands  in  all  cHmates, 
from  tropical  to  cold  temperate,  of  varied  rainfall,  relief,  soil, 
and  mineral  wealth,  and  accessible  to  the  sea.  In  all  these 
respects  the  United  States  approaches  ideal  conditions.  France 
equals  or  surpasses  it  on  a  small  scale.  Russia  lacks  only  sea- 
coast.  China,  AustraHa,  and  Argentina  have  a  hopeful  future. 
Most  of  the  European  states  and  Japan  are  less  favored,  but 
may  extend  their  territories  and  supplement  their  resources  by 
colonization. 

The  geologist  sees  no  reason  to  doubt  that  the  earth  is  des- 
tined to  remain  habitable  for  a  longer  period  in  the  future  than 
it  has  been  in  the  past.    The  human  race  is  still  in  its  infancy, 


MANUFACTURE,   TRADE,   AND   TRANSPORTATION         327 

and  is  barely  beginning  to  realize  the  possibilities  of  its  earthly 
possessions.  Man  is  yet  to  have  his  day,  and  his  kingdom,  in 
which  he  shall  control  the  forces  of  nature  and  have  dominion 
over  the  planet,  is  yet  to  come. 


Fig.  300.  —  A'droplane. 


REFERENCE   MAPS 

Page 

Relief  of  Earth  Crust 22-23 

Volcanoes  and  Earthquake  Areas 68 

Physiographic  Provinces 70-71 

Soils 141 

Mean  Annual  Surface  Temperatures,  Ocean  Currents,  and  Coast  Lines.  .  .160-161 

Mean  Annual  Isotherms 176 

Isotherms  for  July 178 

Isotherms  for  January 179 

Annual  Range  of  Average  Monthly  Temperature 182 

Temperature  Zones • 183 

Temperature  Belts 185 

Isobars  and  Winds  in  July 186 

Isobars  and  Winds  in  January 187 

Ocean  Winds 191 

Weather  Maps,  January  28-31,  1909 200,  202,  203,  205 

Mean  Annual  Rainfall 210-211 

Summer  Rainfall 214 

Winter  Rainfall ^ 215 

Climatic  Regions 224 

Plant  Regions 230 

Density  of  Population 261 

Human  Economies 269 


CONTOUR   MAPS 

From  United  States  Geological  Survey 

Coastal  plain,  drowned  valley,  barrier  beach,  and  lagoon,  New  Jersey 42-43 

Worn-down  plain,  Georgia 46 

Alluvial  plain,  Wabash  River,  Indiana 47 

Glacial  plain  and  cliff  coast,  Illinois 50 

Portion  of  the  High  Plains,  Colorado 51 

A  portion  of  the  Sierra  Nevada,  Cahfornia 55 

Dissected  plateau  and  cliff  coast,  California 57 

Appalachian  ridges  and  water  gap,  Pennsylvania 60 

Hills  of  accumulation,  with  basins,  Wisconsin 61 

A  volcanic  cone;  Mt.  Shasta,  California 65 

Grand  Canon  of  the  Colorado,  Arizona 85 

Maturely  dissected  plateau,  West  Virginia 89 

Niagara  Falls  and  Gorge 92 

328 


INDEX 


172. 


173. 


Absolute  humidity,  193. 
Accumulation,  hills  of,  59. 

plains  of,  49,  52,  53. 
Adaptation,  of  animals,  246-248. 

of  plants,  226-228. 
Adobe  soils,  144. 
Africa,  26,  27,  30. 

coast  of,  162,  167. 
Agassiz,  Lake,  125. 
Age,  of  land  forms,  88-91. 

of  streams,  87-88. 
Aggradation,  defined,  72. 

plains  of,  49,  52,  53. 
Agriculture,  269. 
Air  (see  Atmosphere), 

capacity  of,  193. 

composition  of,  172, 

cooling  of,  194,  195. 

density,  184. 

dust  in,  138,  174. 

moisture  in,  172-174,  193-216. 

pressure,  181,  184,  188. 

relation  to  man,  266. 

saturated,  193. 

temperature  of,  174. 

weight  of,  181. 
Alaska  coast,  map,  163. 
Alaskan  type  of  climate,  225. 
Alcoholic  liquors,  285. 
Alkali  soils,  144. 
Alluvial  cone,  81. 
Alluvial  fan,  81. 
Alluvial  plains,  45,  47-49.  53- 

formation  of,  81-83. 
Alluvial  soils,  142. 
Alpaca,  282. 
Alpine  cHmate,  223. 
Alpine  deserts,  240. 


Alpine  glaciers,  113. 

Alpine  lakes,  126. 

Alpine  type  of  white  race,  260. 

Alps,  the,  59. 

Aluminum,  301. 

Amazon  type  of  climate,  225. 

Amber,  307. 

America   (see   North   America    and    South 

America). 
Animal  migration,  barriers  to,  249. 
Animal  power,  310,  321. 
Animal  realms,  250-254. 
Animals,  adaptations  of,  246-248. 

air  breathers,  243. 

amphibious,  244. 

barriers  to  migration,  249. 

conditions  of  life  on  the  earth,  33-35. 

distribution  of,  249. 

domestic,  270,  277-284,  310,  321. 

effect  of  day  and  night,  14,  15. 

flesh  eaters,  246,  247. 

fliers  and  walkers,  245. 

food  of,  246-248. 

geography  of,  243-254. 

plant  eaters,  246,  247. 

protective  coloration  of,  248. 

realms  of,  250-254. 

relation  to  man,  265. 

use  of  shelter,  248. 

water  breathers,  243. 
Antarctica,  25-27,  31. 

ice  cap  of,  117,  223. 
Anthracite  coal,  312. 
Anticyclone,  189,  199,  201. 
Apples,  276. 
Aqueous  rocks,  37. 
Arctic  Ocean  (see  Sea),  151. 

coasts,  166. 


329 


330 


INDEX 


Argon,  172,  173. 

Arizonan  type  of  climate,  225. 

Artesian  wells,  134,  135. 

Ashes,  volcanic,  67. 

Asia,  26,  27,  28. 

coast  of,  164,  165,  167. 
Ass,  251,  281. 
Atlantic  Ocean  (see  Sea),  150,  159. 

coasts,  166 
Atmosphere  (see  Air),  9,  172-192. 

circulation  of,  S3,  34- 
Australia,  26,  27,  30. 

coast  of,  162,  167. 
Australian  natives,  264. 
AustraHan  realm  of  animals,  253. 

Baltic  type  of  white  race,  260. 

Banana,  267,  269,  276. 

Bar,  80,  84,  129. 

Barley,  271,  273. 

Barometer,  184. 

Barrier  beach,  129,  130. 

Barriers  to  animal  migration,  249. 

Base  level,  88. 

Basin  of  a  stream,  77.     . 

Basins,  defined,  63. 

Bay  bar,  129. 

Bayous,  no. 

Beaches,  129,  130. 

Beaver,  248. 

Bed  rock,  37. 

Beer,  285. 

Bees,  248,  283. 

Beets,  sugar,  274. 

Bernina  and  Roseg  glaciers,  112. 

Bighorn  River,  107. 

Birds,  245-247,  248. 

Bituminous  coal,  312. 

Block  structure,  63,  G4,  67. 

Bluffs,  78. 

Boats,  324,  325. 

Boulder,  glacial,  116. 

Boulder  clay,  121. 

Braided  stream,  106. 

Brandy,  285. 

Brass,  301. 

Breadfruit,  276. 

Breakers,  152,  153. 

Brick,  29S. 


Bridges,  323. 

Broken-block  lands,  63,  64,  67. 

Bronze,  301. 

Buffaloes,  279. 

Building  stone,  298. 

Bunch  grass,  238,  279. 

Burro,  281. 

Bush,  of  Australia,  239. 

Cactus,  228,  240. 

Calendar,  17. 

Californian  type  of  climalc,  225. 

Calms,  190. 

Camels,  247,  281,  291,  321. 

Camphor,  307. 

Campos,  237. 

Canadian  type  of  climate,  225. 

Canals,  ship,  324. 

Canals  and  fiords,  163. 

Canons,  86. 

Capacity  for  vapor,  193. 

Cape  Cod,  map,  129. 

Carabao,  279. 

Carbon  dioxide,  172,  173. 

Caribbean  type  of  climate,  225 

Caribou,  247. 

Carnivorous  animals,  247. 

Cassava,  274. 

Catinga,  234. 

Cattle,  247,  250,  278. 

Caves,  134. 

Cedars,  199,  295. 

Celery,  270. 

Cement,  298. 

Cereal  grains,  271-274. 

Channel  of  a  stream,  77. 

Chapparal,  234. 

Chicle,  307. 

Chimney,  volcanic,  64. 

Chimpanzee,  251,  252. 

Chocolate,  286. 

Circulating  systems  of  the  earth,  SS- 

Cirque,  115. 

Cirrus  clouds,  197. 

Cities,  water  supply,  99. 

Clay,  139,  143- 

constructive  material,  297. 

soil,  143,  144. 
Cliffs,  130,  131. 


INDEX 


33^ 


Climate  (see  Rainfall,  Winds,  etc.),  217- 
225. 

and  civilization,  221. 

east  coast,  219. 

factors  of,  217. 

Mediterranean,  218. 

types  of,  223-225. 

west  coast,  220. 

zones,  217-223. 
Climatic  regions,  223-225. 

map,  224. 
Clothing,  289-292. 
Clouds,  195-197. 
Coal,  312-314. 
Coastal  plains,  44. 
Coast  factors,  166. 
Coasts,  159-167. 

charts  of,  159. 

classification  of,  159. 

map  of,  160,  161. 

rising,  162. 

sinking,  162. 
Cocoa,  285,  286. 
Coconut  palm,  267. 
Coflfee,  285. 
Cold  temperate  zones,  181,  185. 

climate  of,  222,  225. 
Cold  wave,  204. 
Collective  economy,  267. 
CoUuvial  soils,  140. 
Colorado  River,  85,  86. 
Commerce,  320,  325,  326. 
Concrete,  298. 

Condensation  of  water  vapnjr,  194,  195. 
Condiments,  284. 
Conglomerate,  37,  140. 
Conical  projections,  21. 
Coniferous  forests,  234-236. 
Constructive  materials,  294-304. 
Continental  climate,  180,  219. 
Continental  glacier,  11 7- 123. 
Continental  islands,  31. 
Continental  platform,  24,  25,  31. 
Continental  shelf,  24,  25. 
Continents,  26-31. 
Contours,  39. 
Convection,  184. 
Copal,  307. 
Copper,  30X. 


Coral,  157. 

Corn,  271,  272. 

Cotton,  289. 

Crater,  64. 

Crater  Lake,  127. 

Crystalline  rock,  38. 

Cumulus  clouds,  197. 

Currents,  ocean  (see  Ocean  currents). 

Cut-oflf,  no. 

Cyclones,  189,  201. 

efifect  on  climate,  219. 

effect  on  rainfall,  201. 

procession  of,  199. 

tornadoes,  207,  208. 
Cylindrical  projection,  20. 

Date  palm,  276. 
Day,  10,  14,  15. 

civil  and  solar,  15. 
Degradation  defined,  72. 
Dekkan,  233. 
Delta,  49,  83. 
Delta  ports,  168. 
Density  of  air,  184. 
Density  of  population,  map,  261. 
Density  of  sea  water,  152. 
Deposition,  80-83. 
Derwentwater,  125. 
Deserts,  229,  239-242. 
Dew,  194,  198. 
Dew  point,  194. 
Dikes,  83. 
Diseases,  256. 
Dissected  plateau,  58. 
Distributaries,  83. 
Divide,  77. 
Dogs,  282. 
Dolphin,  245. 

Domestic  animals,  270,  277-284,  310,  321. 
Donkey,  281. 
Drainage,  95. 

Drift,  glacial,  116,  1 19-123. 
Drouth  plants,  228. 
Drowned  valleys,  103,  162. 
Drumlins,  121. 
Ducks,  283. 
Dunes,  136-138. 
Dust,  138,  174 
Dyestuffs,  307. 


332 


INDEX 


Earth,  9. 

as  an  organism,  32-35. 

axis  of,  II,  13,  14,  32. 

distribution  of  light  and  heat,  175. 

plan  of  the,  24-31,  34. 

revolution,  11-13,  32. 

rotation,  10,  15,  33. 

structure,  9,  33. 

temperature  of,  32,  34. 
Earth  crust,  24. 

economic  relations  of,  39. 

structure  of,  36. 
Earthquakes,  67-69. 

economic  relations  of,  69. 

map  of  earthquake  areas,  68. 
East  coast  climates,  219. 
Eastern  and  western  hemispheres,  27. 
Ebb  tide,  153. 

Economic  geography,  defined,  265. 
Economic  relations,  of  earthquakes,  6 

of  erosion,  95-98. 

of  fiord  coasts,  164. 

of  glacial  drift,  122. 

of  gradation,  90. 

of  ground  water,  134. 

of  lakes,  128. 

of  mountains,  58. 

of  plains,  52. 

of  plateaus,  53. 

of  rock,  39. 

of  the  sea,  157. 

of  standing  water,  131. 

of  streams,  95-1 11. 

of  sun,  14. 

of  volcanoes,  67. 

of  waterfalls,  94. 

of  winds,  192. 

of  the  world,  32-35. 
Economies,  human,  map  of,  268. 
Electricity,  316. 
Elephants,  247,  248,  252,  282. 
Emu,  253. 

Eolian  plains,  49,  52,  53. 
Eolian  soils,  143. 
Equatorial  calms,  190. 
Equatorial  currents,  156. 
Equatorial  zone,  181,  185.  '^ 

climate  of,  217,  225. 
Equinox,  14. 


Erosion,  76,  81,  84,  86,  87. 

by  wind,  136. 

economic  relations  of,  95-98. 

effect  of,  88-90. 

hills  of,  59. 

rapidity  of,  90. 
Eskers,  121. 
Essential  oils,  307. 
Estuaries,  162. 
Eurasia,  27. 
Europe,  26,  27,  28. 

coast  of,  166,  167. 

glaciation  of,  123. 
Evaporation,  193. 
Explosives,  315. 

Factories,  318,  319. 

Fall  line,  105. 

Faulting,  63,  69. 

Faults,  defined,  63. 

Fertilizers,  146,  304. 

Field  culture,  270. 

Film  water,  147. 

Finger  Lakes,  126. 

Fiord  harbors,  168. 

Fiords,  163,  164,  165. 

Fire,  use  by  man,  308. 

Fish,  243-245. 

Fisheries  in  streams,  100. 

Fishing,  268,  269. 

Flax,  290,  291. 

Flint,  299. 

Flood  plain,  49,  77,  78. 

Floods,  103,  104,  no. 

Floridan  type  of  climate,  225. 

Flow  of  tides,  153. 

Fog,  195. 

Food  supply  of  man,  266. 

Forests,  conservation  of,  297. 

kinds  of,  229-236. 
Fossils,  96. 
Fowl,  283. 
Frost,  198. 
Fruits,  275,  276. 
Fuel,  311-315. 
Furs,  291,  292. 

Garden  culture,  269. 
Gasoline,  315. 
Geese,  283. 


INDEX 


333 


Genesee  River  falls,  loi. 
Geography,  defined,  35. 
Geysers,  133. 

Giraffe,  247,  248,  251,  252. 
Glacial  drift,  116,  1 19-123. 

economic  relations  of,  122. 
Glacial  lakes,  125,  126. 
Glacial  map  of  United  States  and  Canada, 

120. 
Glacial  plains,  49,  53. 
Glacial  soils,  142. 
Glaciers,  11 2-1 23. 
alpine,  113. 
continental,  11 7-1 23. 
valley,  113. 
Glass,  299. 

Globular  projection,  19. 
Gneiss,  38,  139. 
Goats,  247,  250,  280,  291. 
Gold,  302,  303. 
Gorge,  86. 
Gradation,  72. 
by  ground  water,  132-135. 
by  ice,  1 13-123. 
by  running  water,  72-94. 
by  standing  water,  1 28. 
by  winds,  135-138. 
economic  relations  of,  90. 
Grains,  271-274. 
Grand  Canon,  85,  86,  98. 
Granite,  38,  139. 

as  building  stone,  299. 
Grape,  276. 

Grassland,  229,  236-239. 
Gravel,  143. 
Gravity,  33. 
Great  Lakes,  103,  125. 
Greenland,  29,  117,  223. 
Ground,  defined,  36. 
Ground  sea,  132. 
Ground  water,  132. 
economic  relations  of,  134. 
gradation  by,  132-135. 
Guanaco,  282. 
Guano,  304. 
Guinea  fowl,  283. 
Gulf  Stream,  156. 
Gullying,  84,  148. 
Gums,  307. 


Hachured  maps,  40. 
Hailstones,  198. 
Hanging  valleys,  116. 
Harbors,  167-171. 

artificial,  169. 
Heat  (see  Temperature). 
Heat,  earth's,  as  source  of  power,  317. 
Heat,  use  by  man,  308. 
Heat  belts,  177. 
Heat  equator,  212. 
Heat  from  sun,  32,  34. 

distribution  of,  175. 
Hemlock  Lake,  126. 
Herbivorous  animals,  247 
Herding,  277. 
Highlands,  defined,  53. 
High  Plains,  53,  54. 
Highs,  204. 
Hills,  59. 

Hippopotamus,  247,  248,  252. 
Hoe  culture,  269.      *" 
Hog,  247,  281. 
Hollows,  defined,  63. 
Hook,  129. 

Horses,  247,  250,  280,  310. 
Horseshoe  lake,  no. 
Hot  springs,  133. 
Houses,  292,  293. 
Hudson  River,  170. 
Human  economies,  map,  268. 
Human  life,  35. 
Human  species,  255-262. 
Humidity,  193. 
Humus,  36,  144. 
Hunting,  268,  269. 
Hurricanes,  207. 
Hydrosphere,  9, 

Ice,  gradation  by,  1 13-123. 
Icebergs,  115. 
Ice  caps,  117. 
Ice  deserts,  242. 
Ice  sheets,  11 7-1 23. 
Igneous  rock,  38. 

soils  from,  139. 
Indian  Ocean,  151. 
Indo-African  realm  of  animals,  251. 
Insects,  245,  246. 

domesticated,  283,  284. 


334 


INDEX 


Insolation,  266. 
Intemperate  climate,  181,  225. 
Interior  type  of  climate,  225. 
Intermediate  plants,  228. 
Intermont  valley,  62. 
International  date  line,  16. 
Iron,  299-301. 
Irrigation,  102,  104,  148. 
Islands,  31. 

life  on,  254. 
Isobars,  184. 

maps,  186,  187. 
Isotherms,  177. 

maps,  176,  178,  179. 

Jetties,  168. 

Karnes,  121. 
Kangaroo,  253,  254. 
Kerosene,  315. 

Labor  supply,  310. 
Lac,  307. 

Lacustrine  plain,  49. 
Lagoon,  129,  130. 
Lagoon  harbors,  168. 
Lake  plains,  49^. 
Lake  ports,  169. 
Lakes,  124-128. 

alpine,  126. 

economic  relations  of,  128. 

effects  on  a  river,  103. 

glacial,  118,  125,  126. 

horseshoe,  no. 

life  history  of,  127,  128. 

navigation  of,  103. 

volcanic,  127. 
Land  (see  Continents,  Islands,  Gradation, 
etc.),  36-72. 

height  of,  22,  24,  28-31. 

variations  of  area,  24-25. 
Land  and  water  hemispheres,  25-26. 
Land  forms,  41. 

Land  masses,  arrangement  of,  26. 
Landslide,  75- 
Laterite,  145. 
Latitude,  10,  11. 
Laurentian  lakes.  125. 
Laurentian  peneplain,  45,  119. 


Lauterbrunnen,  114. 

Lava,  38,  64. 

Lava  soils,  140. 

Lead,  301. 

Leather,  292. 

Levees,  no,  in. 

Life,  human  (see  Man),  35. 

Life  on  the  earth  (see  Plants,  Animals,  Man), 

33,  34,  35- 
Light,  artificial,  309. 
Light  from  sun,  distribution  of,  175. 
Lignite,  312. 
Limestone,  37. 

as  building  stone,  299. 
Limestone  soils,  140. 
Linen,  290. 
Linseed  oil,  291. 
Lion,  247,  248. 
Lithosphere,  9. 
Llama,  252,  282. 
Llanos,  237. 
Loaded  stream,  79. 
Loams,  144. 
Loess  soils,  144. 
Longitude,  10,  11,  16. 
Los  Angeles  aqueduct,  99. 
Lowlands,  41-53. 
Lows,  204. 
Lugano,  Lake,  126. 
Lumber,  294. 
Lumbering,  296. 

Mahogany,  296. 
Maine  coast,  map,  165. 
Maize,  272. 
Mammals,  247. 
Man,  255-262. 

as  an  animal,  255. 

enemies  of,  256. 

food  supply  of,  266. 

life,  35- 

varieties  and  races,  256-262. 
Man  power,  309,  321. 
Mango,  276. 
Manioc,  269,  274. 
Mantle  rock,  defined,  36. 

formation  of,  72. 

movement  of,  74-76. 

transportation  of,  78 


INDEX 


335 


Manufacture,  318-320. 

conditions  of,  318. 
Maps,  18-21. 

contoured,  39. 

relief,  39- 
Map  projections,  18-21. 
Map  scales,  21. 
Marble,  299. 
Marine  animals,  243. 

Marl,  128.  ,^ 

Marshes,  95,  124-128. 

Mate,  28s,  286. 

Mature  drainage,  95. 

Maturely  dissected  land,  88. 

Maturity  of  streams  and  valleys,  88,  91. 

Medicines,  287-288. 

Mediterranean  climate,  218. 

Mediterranean  Sea,  166. 

Mediterranean  type  of  white  race,  260. 

Mercator's  projection,  20. 

Mercury,  302. 

Meridians,  10,  11. 

Metals,  299-303. 

used  in  electric  batteries,  317. 
Metamorphic  rock,  38. 
Mexican  type  of  climate,  225. 
Migration,  of  animals,  249. 

of  man,  256. 
Mind  sphere,  256. 
Mineral  springs,  133. 
Mining,  294,  299-303,  312-314. 
Mississippi  River,  105-111. 

delta,  82,  168. 
Mississippian  type  of  climate,  225. 
Missouri  River,  106. 
Mollweide's  projection,  20. 
Monkeys,  252,  253. 
Monsoon  forests,  231. 
Monsoons,  192. 
Months,  18. 

Mont  Pelee,  eruption,  67. 
Moon,  17. 

cause  of  tides,  154,  155. 
Moraines,  marginal,  121. 

terminal,  116,  119,  121. 
Mountains,  54-59. 

age  of,  90,  91. 

economic  relations  of,  58. 
Mountain  system,  54. 


Muck  soils,  144. 
Mules,  281. 
Muskegs,  118. 
Musk  ox,  250. 
Mustard,  284. 

Narcotics,  285. 

Natural  gas,  315. 

Natural  resources,  263-266,  326. 

utilization  of,  265. 
Neap  tide,  155. 
New  Guinea,  30. 
New  World,  27. 
New  York,  port  of,  170. 

map,  171. 
Niagara  River,  92,  93,  94. 
Night,  10,  14,  15. 
Nimbus  clouds,  197. 
Nitrate,  304. 
Nitrogen,  172,  173. 

sources  of,  304. 
Nomadic  life,  278. 
North  America,  26,  27,  29. 

coast  of,  163-167. 

glaciation  of,  11 7-1 23. 
Northern  and  southern  continents,  27. 
Northern  realm  of  animals,  250. 
Nunatak  Glacier,  115. 

Oaks,  29s,  296. 

Oasis,  240. 

Oats,  271,  273. 

Ocean  currents,  156,  157. 

effect  on  climate,  156,  157. 

eflFect  on  isotherms,  177. 

map  of,  160,  161. 
Oceanic  basin,  24,  25. 
Oceanic  climate,  151,  180,  220. 
Oceanic  islands,  31,  66. 
Oceans  (see  Sea). 

depth,  150. 

form,  150. 

temperature,  151,  156,  160,  161. 
Ohio  River,  107,  108. 
Oils,  306,  307. 
Old  Faithful  geyser,  133. 
Old  World,  27. 
Olive,  275. 
Onions,  270. 


336 


INDEX 


Opium,  286,  287. 

Oregon  type  of  climate,  225. 

Ores,  299. 

Orthographic  projection,  19. 

Ostrich,  252,  283. 

Outcrop,  defined,  37. 

Oxygen,  172,  173. 

Pacific  Ocean  (see  Sea),  150,  159, 

coast,  163-165. 
Pack  animals,  321. 
Palms,  food  supply,  267. 
Palouse  country,  142. 
Pampas,  239. 
Panama  Canal,  map,  158. 
Paper,  297. 
Parallels,  10,  11. 
Peafowl,  283. 
Peat,  312. 
Peat  soils,  144. 
Peneplain,  45,  88,  90. 
Penguin,  245. 
Petroleum,  314,  315. 
Phosphorus,  sources  of,  305. 
Physiographic  provinces,  69. 

map,  70,  71. 
Piedmont  alluvial  plain,  81. 
Pigeons,  283. 
Pigments,  306. 
Pikes  Peak,  73. 
Pine,  294. 
Pipe,  volcanic,  64. 
Plains,  41-53- 

alluvial,  45,  47-49.  53»  81-83. 

coastal,  44. 

economic  relations  of,  52. 

eolian,  49,  52,  53. 

flood,  49. 

glacial,  49,  53. 

lacustrine,  49. 

lake,  49. 

of  accumulation  or  aggradation,  49,  52, 

53- 
of  degradation,  45. 
peneplain,  45,  88,  90. 
structural,  44. 
wind- worn,  52. 
worn-down,  44,  53. 
Plantain,  276. 


Plantation  culture,  270. 
Plant  regions,  228-242. 

map,  229. 
Plants,  226-242. 

absorb  carbon  dioxide,  173. 

adaptation  of,  226-228. 

as  soil  makers,  146. 

conditions  of  life,  33-35,  226. 

distribution  of,  226-242. 

domestication  of,  269. 

drouth  plants,  228. 

effect  of  day  and  night,  14,  15. 

intermediate  plants,  228. 

relation  to  man,  265. 

relation  to  temperature,  227. 

relation  to  water,  227,  228. 

salt  plants,  228. 

water  plants,  227. 
Plateaus,  53. 

dissected,  58. 

economic  relations  of,  53. 
Playfair's  law,  88. 
Polar  caps,  181,  185. 

climate  of,  222,  225. 
Polar  deserts,  240. 
Polar  type  of  climate,  225. 
Ponds,  124-128. 
Population  of  the  world,  262. 

map,  261. 
Porterage,  321. 
Ports,  167-17 1. 
Potash,  sources  of,  305. 
Potatoes,  274. 
Pottery,  303. 
Poultry,  283. 

Power,  use  by  man,  309-3 17« 
Prairies,  220,  237. 
Precipitation,  197,  209-216. 
Pressure  of  air,  181,  184,  188. 

distribution  of,  188. 
Projections,  18-21. 
Psychosphere,  256. 
Pulque,  285. 

Quartz,  299. 
Quinine,  288. 

Radium,  317. 
Railroads,  324. 


INDEX 


337 


Rainfall,  209-216. 

laws  of,  212-216. 

maps,  210-211,  214,  215. 
Rain  gauge,  198. 
Range  of  temperature,  180, 

map,  182. 
Ravine,  86. 
Redwood,  294. 
Reefs,  157. 
Reindeer,  282. 
Relative  humidity,  193. 
Relief,  defined,  41. 

principal  features  of,  31. 
Relief  map  of  the  world,  22,  23. 
Relief  maps,  39. 
Residual  soil,  139. 
Resins,  307. 
Revived  streams,  90. 
Revolution,  of  earth,  11-13,  32. 
Rice,  271,  273. 
Rift  valleys,  64,  124. 
River  ports,  168. 
Rivers  (see  Streams). 
Roads,  322. 
Rock,  36-39- 

disintegration  of,  72. 

economic  relations  of,  39. 

products  of  disintegration,  139,  140. 
Rock  sphere,  9. 

Rock  waste  (see  Mantle  rock),  72. 
Rodents,  247,  248. 
Root  crops,  274. 
Rotation,  earth's,  10,  15,  33. 
Round  inlets,  169. 
Royal  Gorge,  Colorado,  86. 
Rubber,  291. 
Rum,  285. 
Run-oflF,  77. 
Rye,  271,  273. 

Sahara,  30. 

St.  Lawrence  River,  103. 

Sake,  285. 

Salt,  30s,  306. 

Salt  plants,  228. 

Sand,  143. 

erosion  by,  136. 
Sandstone,  37,  140. 

as  building  stone,  299. 


Saturation,  193. 
Savannah  River,  104,  105. 
Savannas,  217,  236-239. 
Screes,  defined,  75. 
Scrub,  234. 

Sea  (see  Oceans,  Standing  water,  Waves), 
150-159- 

depth  of,  22,  24,  150-151. 

economic  relations  of,  157. 

influence  on  man,  158. 

Hfe  in,  243-245. 

navigation  of,  158. 

tides  in,  1 53-1 55- 
Sea  cliflfs,  130. 
Sea  water,  composition,  151. 

density  of,  152. 

pressure  of,  152. 

temperature,  151,  160,  161. 
Seal,  245,  248. 
Seasons,  11-15,  18,  32,  33, 
Sedentary  soils,  139. 
Sediment,  76,  78-83. 

carried  by  air,  135,  136. 

glacial,  116. 
Sedimentary  rocks,  37. 
Shale,  37,  140. 
Shasta,  Mt.,  65. 
Sheep,  247,  250,  279,  291. 
Shelter,  for  man,  292. 
Ships,  324,  325. 
Silk,  291. 

Silkworm,  283,  284,  291. 
Silt,  143. 
Silver,  302,  303. 
Skerries,  131. 
Snowflakes,  197. 
Soap,  307. 
Soils,  139-149, 

alluvial,  142. 

and  population,  149. 

chemical  constituents  of,  145. 

colluvial,  140. 

composition  of,  143. 

conservation  of,  148. 

defined,  36,  139. 

derived  from  mountains,  59, 

derived  from  volcanoes,  67. 

eolian,  143. 

from  igneous  rocks,  139. 


338 


INDEX 


Soils  {continued),  glacial,  122,  142. 

lava,  140. 

limestone,  140. 

made  by  plants,  146. 

map,  141. 

result  of  transportation,  76. 

sedentary,  139. 

temperature  of,  146. 

transported,  140. 

tropical,  144. 

types  of,  144. 
Soil  wash,  95. 
Soil  water,  147. 
Solstice,  14. 
South  America,  26,  27,  29. 

coasts  of,  162,  163,  167. 
South  American  realm  of  animals,  252. 
Southern  Ocean,  150. 
Sphinx,  eroded,  73. 
Spices,  284. 
Spit,  129. 

Springs,  mineral,  133. 
Spring  tide,  155. 
Spruce,  235,  295. 
Stacks,  131. 
Standard  time,  16. 
Standing  water,  124-131. 

economic  relations  of,  131. 

gradation  by,  128. 
Steam  engine,  311. 
Steel,  300. 

Steppes,  54,  237,  238. 
Stereographic  projection,  19. 
Stimulants,  285. 
Stone,  building,  298. 
Storms,  198,  207-209. 
Strata,  defined,  37. 
Stratus  clouds,  197. 
Streams,  age  of,  88. 

and  relief,  88. 

braided,  106. 

course  of,  76-78,  86-88. 

crookedness  of,  83,  84,  no. 

economic  relations  of,  95-11 1. 

effect  of  lakes  on,  103. 

floods  in,  103,  104,  no. 

loaded,  79. 

navigation  of,  103,  106-111. 

relation  of  valleys  to,  88. 


Streams,  revived,  90. 

routes  of  travel  and  transportation,  100. 

scenery,  98. 

source  of  food  supply,  100. 

source  of  water  supply,  99. 

sources  of,  77. 

speed  of,  79. 

transportation  of  mantle  rock,  76,  78-83. 

utilization  of,  103-111. 

water  power  of,  loi. 
Stream  system,  77,  78. 
Structural  plains,  44. 
Substratum,  265,  266. 
Subtropical  zones,  181,  185. 

climate  of,  218,  225. 
Sugar  beets,  274. 
Sugar  cane,  275. 
Sulphur,  306. 
Sun,  10-14,  34- 

as  direct  source  of  power,  317. 

cause  of  tides,  155. 

economic  relations,  14. 

energy  from,  309. 
Sweet  potato,  274. 
Swine,  247,  281.    . 

Taghannock  Falls,  98. 

Talus,  defined,  75. 

Tapioca,  274. 

Tapir,  252,  253. 

Taro,  274, 

Tasmania,  30. 

Tea,  28s,  286. 

Technical  materials,  304-307. 

Temperate  dry  forest,  234-236. 

Temperate  summer  forest,  232. 

Temperate  zones,  181,  185. 

climate  of,  218,  225. 
Temperature,  174-185. 

effect  of  clouds,  174. 

heat  belts,  177. 

range  of,  180,  182. 
Temperature  belts,  181. 

map,  185. 
Temperature  zones,  180,  181. 

map,  183. 
Terminal  moraines,  116,  119. 
Textiles,  289. 
Thorn  forest,  234. 


INDEX 


339 


Thorn  scrub,  234. 
Thunderstorms,  209. 
Tidal  power,  317. 
Tides,  153-155- 
Timber,  294. 
Timber  Hne,  defined,  58. 
Tin,  301. 
Tobacco,  286. 
Toddy,  285. 
Tools,  303,  304. 
Tornadoes,  208. 
Trade,  320,  325,  326, 
Trade  winds,  190. 

relation  to  rainfall,  213. 
Transportation  of  freight,  320-325. 
Transportation   of    sediment,    by   glaciers, 
115-116. 

by  streams,  75,  76,  78. 

by  winds,  135,  136. 
Transported  soils,  140. 
Trapping,  268,  269. 
Tributaries,  76. 
Tropical  calms,  190. 
Tropical  dry  forest,  233. 
Tropical  rain  forest,  229. 
Tropical  soils,  144. 
Tundras,  223,  241,  242. 
Tunnels,  323,  324. 
Turkey,  domestic  bird,  283. 
Turpentine,  307. 
Typhoons,  208. 

Undertow,  130,  153. 

United  States  Geological  Survey  maps,  39. 

Uplands,  53. 

Valleys,  62. 

age  of,  88. 

drowned,  103,  162. 

forms  of,  84-88,  77. 

glaciated,  114,  115,  116,  117. 

hanging,  116. 

relation  to  streams,  88. 

upper,  middle,  and  lower  parts  of,  86. 
Vaix>r,  172,  174,  193,  194. 

condensation  of,  194,  195. 
Vegetable  growing,  270. 
Vehicles,  322. 
Veldt,  239. 


Vicuiia,  282, 
Vinegar,  284. 
Volcanic  cone,  64. 
Volcanic  lakes,  127. 
Volcanic'lands,  64-68. 
Volcanoes,  64-68. 

economic  relations  of,  67. 

map,  68, 

Walrus,  245. 

Water  (see  Streams,  Sea,  Lakes,  Standing 
water.  Rainfall,  etc.),  9,  24-26. 

animals  living  in,  243-245. 

circulation  of,  33,  34. 

forms  of,  32. 

needed  by  plants,  147. 

transportation  of  freight  by,  324. 
Water  buflfalo,  279. 
Waterfalls,  93. 

economic  relations  of,  94. 
Water  plants,  227. 

Water  power,  59,  loi,  104,  105,  315-317. 
Water  sphere,  9. 
Water  supply  of  cities,  98,  99. 
Water  table,  132,  147. 
Water  vapor,  172,  174,  193,  194. 

condensation  of,  194,  195. 
Waterways,  325. 
Watkins  Glen,  96. 
Wave  power,  317. 
Waves,  description  of,  152. 

gradation  by,  130. 

work  of,  153. 
Weather  bureau,  199,  206. 
Weather  maps,  199. 
Weather  maps  for  January,  28-31,    1909, 

200,  202,  203,  205. 
Weathering,  72. 
Wells,  134. 

West  coast  climates,  220. 
Westerly  winds,  190. 
Whales,  245,  306-307. 
Wheat,  271. 
Whisky,  285. 
Wind  belts,  189. 
Wind  power,  311. 
Winds,  184-192. 

cyclones  and  anticyclones,  189,  201. 

economic  relations  of,  192. 


340 


INDEX 


Winds  (continued),  effect  on  isotherms,  177. 

erosion  by,  136. 

gradation  by,  135-138. 

laws  of,  184,  188-192. 

maps  of,  186,  187,  191. 

tornadoes,  208. 
Wind-worn  plain,  52. 
Wines,  276,  285. 
Wood,  294,  311. 
Woodland,  228. 

dry,  233-236. 

wet,  229-233. 
Wool,  280,  291. 
World  economy,  32-35. 


Worn-down  plains,  44,  53. 

Yak,  279. 

Yam,  267,  269,  274. 

Year,  17. 

Yosemite  Valley,  97,  98. 

Young  stream,  87. 

Youth  of  land  forms,  88-91. 

Zambezi  River,  93,  94. 
Zebra,  248,  251,  252. 
Zebu,  279. 
Zinc,  301. 

Zones  of  temperature,  180,  181. 
map,  183. 


ALT' 


-"-TT'oF     25     CENTS 
AN    ^NlTlAL^^^^^o^  ---h7p^."-- 

WIL-L.  BE  ASSESSED  ^^^      7"hc  FOURTH 

DAY     AND    TO    «1"  ___^^===r= 

OVERDUE.  -^' 


DEC   W  1S32     9^  n  ^^^ 

^^g. 61971  80 
REC'DLD    JAI^  2 3  71 -12 AM  3  5 

SEP  19  1933 

FEB  ^r- 


l5Dec 


5fTF 


TjECS    1955  LU| 


LD  2l-50?H-»,- 


-8,-32 


l!!j;:;i>ti;i 


UNIVeiSITY  OF  CAUFOI^|A.I4^RARY     ?^t- 


is 


k 


